PCB4522- EXAM 4 STUDY GUIDE

How do you pack a large amount of DNA in small volumes?

What is the density of the packaging of DNA for the following? bacteria eukaryotic nucleus phage T4

Define packaging ratio.

What is the packing ratio number?

What is the ratio of interphase chromatin?

What is the nuclear DNA length of a human nucleus?

What is a major difference between filamentous and icosahedron packaging type?

What is the function of terminase?

What role does the IHF play?

The bacterial nucleoid is _______% DNA by mass while the eukaryotic chromosomes is _______% by mass.

What unfolds DNA?

What is the average density of supercoiling?

How are bacterial genomes organized?

List four DNA binding proteins in E.coli that participate in the packaging of bacteria

Where is DNA located in bacteria?

Are there any histones in bacteria?

Loops are also known as

Why is there supercoiling?

How are 10 nm fiber released?

How do you relax the tension of a supercoil?

The loop(domain) structure is about __________kb and goes attached to a central proteinaceous core ____________.

T/F In Eukaryotes, 50% is DNA and 50%is protein based. If the scaffold is about 8% of the protein then the rest (42%) is histone.

What is a similarity in packaging between bacteria and eukaryotes?

The base of the DNA loops attach to the nuclear matrix that is comprised of lamen proteins is called __________ and also known as _______________ ____________ _____________.

Does MARS have a consensus sequence?

MARs have sites for _____ binding and recognition sites for ____________; therefore, it functions in opening the chromatin and DNA tension.

What controls the degree of supercoiling in eukaryotes?

What functions in opening the chromatin and DNA tension?

What is the difference between interphase chromatin and mitotic chromosomes?

The interphase chromatin has both Euchromatin and Heterochromatin, which of the two is more condensed?

Which of the two is accessible for transcription? (Euchromatin or Heterochromatin)

T/F Euchromatin is composed of only 30 nm.

There are two forms that make up the heterochromatin, which of the two serve as a structural element of the chromosome and is composed of regions that are not expressed since they remain condensed.

Which form of heterochromatin has entire chromosomes that are inactive in one cell lineage?

The lampbrush chromosome is known to be about ~___ times less packed since the loop out regions are heavily transcribed and is formed during _____ _______ in amphibians such as a newt.

The lampbrush chromosome correspond to places that are

What is the direction of transcription when a lampbrush chromosome is present?

The polytene chromosome is observed in larval salivary gland interphase nuclei of a drosophila, with a packaging ratio of ~__. Transcriptionally active bands are called _____ and an extreme case of this is called ________ _______. The chromosome builds up _____ _____ running longitudinally by doubling the chromosome up to__times.

Where would you go looking for lampbrush chromosomes? around the dumpster for a large supermarket. under a rock in a stream in the dirty laundry hamper near a deep sea thermal vent

T/F Each chromosome contains a single duplex strand of DNA and is replicated a semi-conservative mechanism.

Each chromatid consists of a fiber with a diameter of _____nm and higher.

T/F Interphase chromatin is a mixture of the 10 nm and 30 nm fibers.

The sites at the two regions where microtubules are attached to either the centromere (at the kinetochore) and/or the centrioles are called _______ ______ _______ or _ _ _ _.

What is found in the cytoplasm of metazoan cells, but not in plants and fungi?

T/F MTOCs are present in all eukaryotes.

Centromeres are essential for segregation, but what holds the two chromatids together?

25. There are three types of centromeres, name them.

During telophase a fragment breaks off and stays behind, this fragment is called _____ because it does not get attached to a mitotic spindle since it does not have its own centromere.

There is a fibrous structure found at the centromere that is attached to the microtubule during mitosis. What is this structure called?

Which structure provides the MTOC for the chromosome?

Yeast has an unusual kinetochore called the ____complex

Centromeres can take a variety of forms: recite them. Insects, mammals and plants have what type of centromere? Nematodes have what type of centromere? Budding yeast have what type of centromere?

There are alternating patterns of H3 ______and ______tetramers within the centromere. The location of the _____ ________ seems to be epigenetically controlled and are involved in recruiting proteins that form the _________.

CEN DNA sequence composition in yeast consist about ~120 bp and is divided in 3 parts: CDE-I, CDE-II, and CDE-III. Which of the three is the longest and is AT rich? Which of the three is highly conserved, and why?

The minimal sequence that can confer mitotic stability on a plasmid (yeast) is known as:

What is an example of the point centromere?

Which of the following has the most critical function thus a single mutation in it is disruptive? CDE I CDE II CDE III

What is the MTOC made up of?

Mutations in _________ severely disrupt segregation and prevent CBF3 binding. CDE I CDE II CDE III

CBF1 (centromere binding factor 1) binds which of the CDE? What about CBF3?

Which of the following is associated with intrinsic bending? CDE I CDE II CDE III

What is the human homolog to yeast Cse4p?

Which protein found at the CEN resembles a histone?

Cse4p in yeast is the homolog for which type of histone?

In Yeast, Cse4p resembles a nucleosome: how many turns does DNA wrap around the Cse4p?

Which histone is required to form 10nm fiber coil into a 30nm fiber, and is not part of a nucleosome?

What protects chromosome ends from fusing due to the activity of repair systems and the ends must be disguised so they do not look like ds-breaks?

Chromosomes ends are disguised so they don't look like double strand break causing repair mechanisms to fuse both ends and from DNase activity. The telomere has a consistent repeat what is it? Hint:C>1( / )1-4

What are the two ways to generate a GT rich strand overhang?

What is the telomerase in humans?

Many human cell lines can be immortalized by the introduction of the _________. While other tissue types require _______ plus the ______________ antigen to be immortalized.

Normal tissue types can be transformed to oncogenic lines by introduction of what three genes?

What protein keeps the G-T protruding 3' end from going to far((prevents excessive of the 5' end)?

What protein binds to the telomere repeats and what two proteins does it recruit?

What extends the protruding 3' end?

What forms as a result of strand invasion?

When the the tail of the telomere is paired with the homologous strand it forms?

Which telomere protein makes complex with other proteins & stabilizes chromosome ends?

What protects the ends of chromosomes from recombination repair which would try to fuse the ends?

Which protein is critical to forming the T-Loop?

The Shelterin complex binds to the end of the telomere and is involved in

Which protein binds to ssDNA of the G-T strand?

Which protein triggers heterochromatin?

What are three major roles of the telomere?

What protein identifies the G-hairpins and causes the telomerase to move forward?

What is a reverse transcriptase that carries its own RNA template?

How does telomerase position itself?

The telomerase extends which strand?

How long is the template that the telomerase carries? Its equivalent to?

The length of the protruding G-T 3" end remains constant. In humans the GT strand is 150 nt, how is this controlled?

How many generations could plants (arabidopsis) survive if telomerase is absent?

What happens if you mutate telomerase?

Telomeres shorten about _____ bp per generation in plants.

How does telomeres form heterochromatin?

What protein mimics lamen that is found in nuclear matrix?

Which protein binds CnA/T repeats at telomeres to initiate heterochromatin formation?

Which protein(s) binds to Step1 protein, histone 3 and 4 tails?

Which protein deacetylates the histone tails?

Which protein may be responsible for telomere clustering to the nuclear periphery?

How many nucleotides per nucleosome?

How much of chromatin is histones?

What are two of the most highly conserved proteins in evolution, even in archaea till this day?

How many turns is DNA wound around the outside of the core particle?

Which fiber is known as the beads on a string?

What is the packaging ratio of 10 nm fiber histones?

What are examples of the 10 nm fiber histones?

How are 30 nm fibers made?

Which fiber requires the nucleosomal histones with the addition of histone H1?

What is the packaging ratio of 30 nm fiber?

What is the final packaging ratio for 50nm and above in euchromatin? What about mitotic chromosome & heterochromatin?

How many base pair does a mononucleosome have when low levels of DNase is present? What about in very high levels of DNase activity? The highest level of DNase activity is known as ___ ___?

How many bp of DNA does a nucleosome contain and what how many histones are present?

What is average distance between nucleosomes?

What is the length of the core DNA that is found on the core particles produced by PROLONGED digestion with micrococcal nuclease?

What would the average size of the fragments of chromatin be if you added just enough nuclease to hit once per nucleosome? 146 bp 165 bp 200 bp

How many bp does it take to make two turns around th octomer?

H1 does not participate in forming the histone octamer, so where does it mostly bind to?

Which species lacks H1 histone and the 30 nm fiber? Why?

Nucleosomal DNA is divided into the ____DNA and_____DNA

Which histones interact with each other and hold the tetramer together?

Which histone sits behind H3?

Which histones form the core?

Which histones form the cap?

What does a histone fold have?

How many nucleosomes per turn does the 30nm fiber have?

Would a zig zag two-start helix be present in Archaea?

The six nucleosomes in the 30 nm fiber are organized into a

Which histone is required for formation of the STABLE 30nm fiber?

The ________-terminal tails are flexible and extend from the core and are sites of modification normally known as the ______________ _____________________.

Why do Archaea have no histone tails?

What are three most common types modifications?

Which kind of acetylation is associated with gene activation? HAT or HDAC

Which kind of acetylation is associated with gene repression? HAT or HDAC

What does HAT stand for?

What does HDAC stand for?

What are the names of modifications that deal with methylation?

What are the names of modifications that deal with phosphorylation?

What neutralizes the positive charge on lysine?

What introduces negative charges on serine?

T/F The positive charge on lysine is neutralized upon acetylation, while methylated lysine and arginine retain their positive charges.

The pattern of histone modification associatied with gene activation state is known as ?

What kinds of modifications are associated with transcription activation?

What kinds of modifications are associated with nucleosome assembly?

What is the main reason that when you acetylate lysine it will cause the chromatin to decondense?

How many methyl groups are required to successfully neutralize the positive charge?

What does HDAC do?

Are histone octamers conserved or preassembled during replication?

What are the accessory proteins that are required to assist the assembly of nucleosomes? (two that act as chaperones)

Which proteins are associated with replication dependent assembly?

What is the name of the protein required for DNA-dependent nucleosome assembly that is recruited by the clamp (PCNA)?

Once DNA has been replication, nuclesomes assemble. Where does CAF1 bind to and what is added to that complex?

T/F Nucleosome assembly in vivo: Step 1- DNA wraps around H3/H4 tetramer Step 2- One H2A/H2B dimers are bound to form the octamer.

In replication dependent nuclesome assembly, which auxillary factor assists CAF1 in nucleosome reassembly on the leading strand(de novo assembly), and participates in transferring old nucleosome on lagging strand (parental histone transfer)

What are two pathways of nucleosome assembly?

Some extremely heavily transcribed genes appear to be so active in transcription they have no nucleosomes structure at all. What kinds of genes are they?

Which genome can be extracted from cells with nucleosme attached and transcription in progress?

What proteins are associated with replication independent nucleosome assembly?

What protein displaces histone octamers during transcription by releasing H2A/H2B dimers and remains attached to the H2A/H2B dimers after transcription to facilitate next round of transcription?

In replication independent nucleosome assembly: what is the name of the histone that slowly replaces H3 in non differentiating cells, after transcription and after repair?

What is the name of the protein that is used in independent nucleosome assembly and is not recruited by a clamp nor is it bound to it?

What does yeast use instead of H3?

What do mammals use instead of H3?

An enhancer activates a promoter in its vicinity, but can be blocked from doing so by an ________________________________ located between them.

What do insulators do?

In Drosophila heat shock locus the ________ and ________ serve as insulators that do not directly regulate gene activity but function as barriers.

T/F RNA pol II and insulator proteins do not co-occupy the same regions.

What protein binds to the scs/scs' insulators found in Drosophila heat shock locus?

When are histone variants used?

Eukaryotic transcription occurs on chromatin, not naked DNA as in bacteria. What are two requirements for transcription to occur?

Eukaryotic RNA polymerase cannot read DNA, so how does it initiate transcription?

What are basal transcription factors?

What is a core promoter?

DNA of the promoter that corresponds to the first nucleotide transcribed. RNA pol contacts it directly, but does not select it.

What does the full promoter contain?

What are the three major RNA polymerases that eukaryotes have? What are their function?

Rank the RNA polymerases in order of most active to least active.

Which RNA polymerase mRNA is the least abundant RNA in the cytoplasm and are internal?

T/F All eukaryotic RNA polymerases have ?12 subunits and are aggregates of >500 kD.

What is the difference between the subunits in Eukaryotes and Archae?

Which RNA polymerase accounts for most cellular RNA synthesis and resides in the nucleolus?

Which RNA polymerase accounts for most of the remaining activity in the cell and it sensitive to a- amanitin?

Core Promoters for pol I and II are _______ of the start point. Some pol III promoters are ________ to the transcribed region.

Do eukaryotic RNA polymerases have a sigma like in bacteria?

The largest subunit in RNA polymerase __ has a CTD (carboxy-terminal domain) consisting of multiple repeats of a heptamer. What subunit is that?

What serves as a trigger to transition from initiation to elongation in eukaryotic transcription?

What two proteins bind to RNA pol I?

Which core-binding factor consisting of TBP and 3 other proteins is involved in positioning the RNA polymerase and directs a low level of constitutive transcription?

Which upstream binding factor consisting of a single peptide ensures high-frequency initiation?

What transcription factor is involved in initiation by all three RNA polymerases?

The factor ____________ wraps DNA around a protein structure to bring the core and UPE into proximity.

RNA polymerase binds to the ___________ complex at the core promoter.

Which of the following is responsible for determining the start point of transcription? UBF Sigma 70 RNA pol I SL1

What is the commitment factor for Pol III promoters?

What enables TFIIIB to bind at the startpoint of type 1 promoters by binding to the concensus sequences?

TFIIIB has _________ as one subunit and enables RNA polymerase to bind. Positions the polymerase.

What determines where polymerase should start?

What is the major difference between type 1 and type 2 promoters?

TFIIIA and TFIIIC are ______________________________.Their only role is to direct TFIIIB to the right location. These can be removed once TFIIIB has bound and transcription can still proceed correctly.

What is the only true initiation factor?

Which of the three assembly factors have a Zinc Finger? and Which has a similar size to the RNA pol?

What two other subunits does TFIIIB have other than TBP and what are their functions?

Which TFIIIB subunit is similar to sigma?

Type 1 pol III promoter is found only in __________________.

Where does the (HAT) co-activator bind? Directly on DNA or on trans-activators?

Where does RNA pol II bind?

Where does the repressor HDAC bind?

What are the steps of gene activation?

What is the function of the trans-activators/enhancers?

What basal factors does RNA polymerase II require to initiate transcription?

What do RNA pol II startpoint promoters look like? Do they have a special sequence?

The TATA box is a common component of RNA polymerase _____ promoters. It consists of an ____ rich octamer locates ______ bp upstream of the startpoint?

The _____ is a common component of RNA polymerase II promoters that do not contain a TATA box?

What does the minimal promoter for RNA polymerase II include?

List the commitment factor for pol I, II and III

What is involved in initiation of RNA synthesis of all pol II promoters and forms the preinitiation complex?

Transactivators, transfactors are known to be ________________ ________________, which bind upstream elements are are specific to different promoters.

A type of upstream factor that controls highly regulated (inducible) transcription; binds to a response element, is known as?

T/F Cis-elements may be located upstream, downstream, or in introns. Most commonly found upstream.

Elements may be _____________ in distribution, or organized in clusters called ___________.

The two types of transcription are Basal and Activated. Which has low level activity and which has High level of activity? Which one only requires a minimal promoter? Which one requires Upstream factors/cis-elements?

The minimal promoter is from the -__ to +__.

Key step in activated transcription performed by ________________ __________________.

What does TFIID consist of?

Where does TBP bind to the TATA box, in the minor groove or major groove?

What forms a saddle around the DNA and bends it by 80 degrees?

Some of the TAFs resemble histones and may form a structure resembling a histone octamer. What does TAF stand for? How many TAFs are within the TFIID?

What basal factor binds to the C terminal stirrup? What about N terminal stirrup?

What elements determine the polarity of transcription?

TBP forms a saddle around the DNA and bends it by how many degrees? It does this by introducing kinks in the DNA that are the result from insertions of how 2 _________.

What are the structures of the TFIIB?( hint: 4 structures)

What protrudes into RNA exit pore of RNA pol II and interacts with 5' end of transcript?

What melts the promoter 20 bp upstream from TATAA?

What contacts the -8 of the initiator element?

What has structural similarities and performs many of the functions of sigma in eukaryotes?

What contacts position -1?

The ________ and _________ contact the 5-end of the nascent transcript RNA and block its entry into the RNA exit channel similarly to sigma domain 3.2.

The TFIIB N-term protrudes into RNA pol ____ ____.

What is required for the recruitment of the add poly(A) complex involved in termination?

What are basal factors that bind to RNA polymerase?

Which basal factor plays a role in transcriptin and nucleotide excision repair?

Why are TFIIE and TFIIH required during initiation?

What is required for elongation to begin?

What plays a major role in phosphorylation CTD?

List the 6 Involvements of the CTD of the largest subunit of RNA pol II in RNA processing.

Which of the following is NOT a function of the CTD? Recruits the polyadenylation enzymes Transition from initiation to elongation Recruits enzymes to add Gm7 Melts the promoter

Mutations in the ______ component of the TFIIH cause three types of human diseases.

What roles does TFIIH play?

T/F Gene Expression Is not associated with De-methylation of the DNA at the 5? end of the gene (promoter) and is not necessary for transcription.

Methylation of the C in a CpG doublet leads to? why?

What does MeCP2 do?

How many CpG islands are in the human genome?

The density of a CpG is about ~_/100bp. The density of a CpG island is about ~_ _/100bp.

Drosophila and Nematodes methylation differences are?

Methylation of CpG islands seems to regulate which type of genes? Environmentally inducible Those activated by strong enhancers Constitutive genes

Which of the following protein bind to methylated CpG islands? MeCP1 and MeCP2 SCAFs P-TEFb Mfd

TFIID is about ~800 kD, is this larger than RNA Pol II?

Does TBP of TFIID bind to the TATAA promoters?

Which TAF is the largest?

Which TAF is the smallest?

Whic commitment factor does not bind to TATA even though it has a TATA domain?

Which component of TFIID blocks TBP from binding TATA?

What induces genes in eukaryotes?

Does Archaea have TAFs?

List the four functions of TFIID

Which TAFs cooperate together to recognize initiator region?

Which TAFs cooperate together to recognize the DPE (downstream promoter element)?

Which TAFs serve as targets for recruitment transactivator proteins (acidic activators)?

Which TAFs contact TFIIF?

Which TAF contacts TFIIA?

TAF1 has 3 enzymatic activities what are they?

What uses the N-terminal to fold around and form a mimic of the TATA sequence?

TAF7 is blocking the HAT activity that will de-condenses the chromatin what events cause Taf7 to lose affinity for TAF1 and bind to TBP?

Which TAF have histone fold like structures?

Which TAF resembles H3/H4?

Which TAF resembles H2A/H2B?

TFIID Promoters that lack TATA are ___________.

TBP can function with SAGA and PCAf.

SAGA is the complex in _____________, while PCAF is the complex in ________________.

Those that have TATAA do not require ______

Whats the name of the transactivator that recruits SAGA but is unable to recruit TF2D?

What subunit has the HAT in the following? TFIID SAGA PCAF

What complexes have the HAT activity?

Which of the TFIIF shows similarity to bacterial sigma factor domains 2 and 3.2?

What is required for RNA pol II to join the PIC?

T/F The CTD does not bind the mediator.

TFIIF assists promoter targeting when it binds onto who?

Who puts the Phosphate groups onto the CTD?

Who stimulates a phosphatase to remove them? when do we see this stimulation?(hint: is it at the PIC or not at the PIC)

TFIIF is bound to the polymerase, who is recruited after, TFIIE or TFIIH?

Who modulates and assists TFIIH kinase, ATPase, helicase and promoter melting activities?

Which protein is involved in initiation and elongation and decreases pausing and protects elongation complex from arrest?

What has to occur in order for the polymerase to leave the pre-initiation complex?

List the function of TFIIE.

T/F TFIIE-alpha is also found in Archaea.

Which complex is involved in promoter melting through helicase activity, promoter clearance by CTA kinase activity and functions in nucleotide excision repair?

What things do Archaea have that eukaryotes have?

TFIIH has a promoter melting and a Nucleotide excision repair. Both are helicases activity. What are their directions (hint: 5'to 3' or 3' to 5')

What happens when TFIIH phosphorylates the CTD?

What phosphorylates the CTD? Explain the process.

What is the CAK homolog in yeast?

CTD Kinase also known as _ _ _ _ is regulated by ______ _ which in turn its regulated by _____ module of the mediator while _____ serves as the structural subunit of CAK.

How does the process work when TFIIH is involved in nucleotide excision repair?

CDK8 phosphorylates _____ and shuts off _________.

Only one structure of the TFIIH is involved in both transcription and NER. What is the structure?

Who facilitates the reaction of forming 1st phosphodiester?

Which complexes melt the transcription start site using one of its helicases (3' to 5')?

What serves as the trigger that transitions from initiation to elongation?

The multistep assembly: Activator binds first and recruits _ who recruits A or B either order_ joins to pol2 forming Pol2/_ complex and joins PIC then_ joins the complex and recruits _.

Transcription cycle: ______ phosphorylates the CTD and the mediator loses affinity for the CTD , the CTD dislodges from TBP and from Mediator. RNA pol II initiates and clears the promoter then later the CTD is dephosphorylated by a phosphatase activity stimulated by______ (in the absence of _____). Termination: RNA pol II/TFIIF complex leaves the template, forms complex with the________ and reinitiates with the CTD in the underphosphorylated state.

Which factors remain at the promoter and which leave?

Mediator only attaches to the _______________________ CTD.

When does the mediator lose affinity for the CTD?

A large complex of proteins known as the _________________ is also part of the preinitiation complex.

T/F The Mediator is called an integrator of positive and negative signals, which determines the amplitude of transcription.

Mediator is in an extended conformation, with ______, _____, and ____domains clearly distinguishable.

What helps the mediator bind to the CTD?

The mediator (in yeast) is divided in two subunit groups: SRB ( suppressor of RNA pol B (II)), and ____, which its functions is still unknown.

What is the target of Cdk8?

What happens if you delete or mutate the SRB4 subunit from the head?

Mediator subunits can be biochemically purified as modulues like:

What is found in the middle of the mediator?

What is the function of Gal 11 (tail)?

What happens if you mutate or delete Sin4 from the tail?

What are the Cdk8/CycC SRB names? (Hint: Srb__/Srb__ respectively)

What role does Srb10(Cdk8) and Srb11 (CycC) play?

What are two ways to purify the mediator?

Which of the following is dissociable? (Cdk8)Srb10 (CycC)Srb11

What are two ways that the mediator inhibits transcription?

What do proteins disrupt nucleosome structure resulting in 30 fold increase in binding of transactivator proteins. (require ATP)?

What triggers the opening of the clamp?

What determines the startpoint for transcription?

What determines the frequency of transcription?

What connects activators to basal factors?

The role of the _______________ domain is to bring the transcription-activation domain into the vicinity of the promoter.

Nuclear receptors are the same as ______________ ______________ and they also have a zinc containing binding domain.

What is a unique feature of the zinc finger?

How could you build a transcription factor if its going to be specific to any gene, if could only read 3 bases?

Three zinc fingers fit into the ___________ groove.

T/F Polydactyl zinc finger proteins can deliver any protein to a specific genomic address.

Steroid receptors have two zinc modules, one bind _________, the other involved in ________________. Each module contains __ zinc ion and __ cysteines.

What must steroid receptors do to activate transport to the nucleus?

What are two things that determine which steroid receptor binds to which particular promoter?

What is an amphipathic helix?

T/F Acidic activators are a major class and may be the only one in yeast.

How does glucocorticoid receptor activate transcription?

How happens if the interaction between GR and Hsp90 is not disrupted?

What happens when glucocorticoid binds to the receptor?

One property determines their activity for the whole group called __________ _____________________, when they should be active, they end up going to the nucleus otherwise they are sequestered in the cytoplasm.

Estrogen receptor recruits a coactivator called __________

What must happen for the coactivator P160 to be active?

How could P160 bind to the binding pocket if it is protected by helix 12?

What happens when you bind estrogen to the binding pocket?

What blocks helix 12 so you cant get activation by estrogen?

How does taxmoxifen block further access of P160?

_________ _____________ do not directly recruit members of the preinitiation complex. Instead, they make contact with _____________, which in turn, recruit basal factors.

T/F P160 recruits HAT complexes since it has no HAT activity.

How do steroids activate transcription.

What leaves once the mediator arrives during steroid transcription?

Which hormones form homodimers and recognize the sequence TGTTCT?

Which hormones form heterodimers and recognize half elements TGACCT?`

Which of the following half sites are palindromes? homodimer heterodimer

Homodimer steroid activators bind the ____ sequence with a difference in spacing.

Heterodimer steroid activators ________ determines specific recognition.

Which have head to head receptors and which have head to tail receptors?

The _________ receptor and the ________ receptor bind the SMRT corepressor at the promoter in the absence of ligand. Binding of the ligand reduces the affinity for the corepressor and allows binding to coactivators.

Why happens when the thyroid hormone is not around?

What happens when the thyroid hormone arrives?

Which hormones act both as activators and repressors?

Hormone activated transcription in plants: What triggers the activation of the glucosinolate pathway in plants?

How is insect feeding activate transcription?

How does the Topless corerepressor repress? What does it use?