T.13 Regulación durante la elongación de la transcripción

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Questions and Answers

What is the primary function of the sigma factor in the initiation complex?

To recognize and bind to specific promoter sequences (correct)

To bind to the RNA polymerase and position it for transcription initiation

To stimulate transcriptional elongation

To transcribe DNA into RNA

What is the role of the catalytic core enzyme in RNA polymerase?

To transcribe DNA into RNA (correct)

To recognize and bind to specific promoter sequences

To modulate gene expression

To stimulate transcriptional elongation

Which of the following factors can influence transcriptional elongation rates?

RNA polymerase processivity and presence of transcriptional elongation factors (correct)

Sequence-specific features of the DNA template only

Presence of transcriptional initiation factors

Chromatin structure and accessibility only

What is the primary function of transcriptional pausing?

To allow for temporal regulation of gene expression Signup and view all the answers

What is the effect of NusA on transcriptional elongation?

Stimulates transcriptional elongation Signup and view all the answers

What is the function of Mfd in transcriptional elongation?

Stimulates transcriptional proofreading and repair Signup and view all the answers

Where can regulation of transcription probably occur?

Anywhere along the transcription process Signup and view all the answers

What is the role of the protein Tat in transcriptional elongation?

To bind to the TAR sequence in the mRNA Signup and view all the answers

What is the purpose of phosphorylation at Ser2 in RNA polymerase?

To allow escape from the promoter Signup and view all the answers

What happens when RNA polymerase encounters the first nucleosome?

It is paused Signup and view all the answers

What is the outcome when RNA polymerase is poised at the nucleosome?

It can rapidly continue transcribing Signup and view all the answers

What is the general trend in regulation of transcriptional elongation?

It is the rule Signup and view all the answers

What is the duration of pausing in transcriptional elongation?

Sometimes short, sometimes long Signup and view all the answers

What is the significance of the TAR sequence in transcriptional elongation?

It is a binding site for the Tat protein Signup and view all the answers

What is the outcome when RNA polymerase is not phosphorylated at Ser2?

It is paused Signup and view all the answers

What is the purpose of the P-TEF complex in transcriptional elongation?

To phosphorylate RNA polymerase Signup and view all the answers

What is the result of transcriptional pausing at the nucleosome?

The RNA polymerase waits for permission to continue Signup and view all the answers

What is the role of P-TEFb in transcription elongation?

To regulate the elongation process by phosphorylating the CTD of RNAP II Signup and view all the answers

What is the effect of DSIF on transcription elongation?

It reduces the activity of P-TEFb, leading to transcriptional pausing Signup and view all the answers

How does P-TEFb interact with the RNA polymerase?

Through a direct interaction with the CTD of RNAP II Signup and view all the answers

What is the role of CycT1 in transcription elongation?

To mediate the interaction between P-TEFb and the CTD of RNAP II Signup and view all the answers

What is the effect of HEXIM on P-TEFb activity?

It inhibits P-TEFb, leading to transcriptional pausing Signup and view all the answers

What is the characteristic of genes with paused polymerases at the +1 nucleosome?

They are genes that respond to external stimuli Signup and view all the answers

What is the role of repressors in transcription elongation?

To block the recruitment of P-TEFb to the transcription complex Signup and view all the answers

What is the characteristic of promoters with paused polymerases?

They are typically associated with genes that respond to external stimuli Signup and view all the answers

What is the role of activators in transcription elongation?

To attract P-TEFb to the transcription complex Signup and view all the answers

What is the characteristic of TATA-like promoters?

They have high levels of CpG islands and are typically associated with housekeeping genes Signup and view all the answers

Study Notes

Regulación de la transcripción

Initiation Complex

Formation of a complex between RNA polymerase, sigma factor, and DNA promoter region
Sigma factor recognizes and binds to specific promoter sequences
RNA polymerase binds to the promoter region, positioning it for transcription initiation
Initiation complex formation is a key regulatory step in transcription

RNA Polymerase

Responsible for transcribing DNA into RNA
Composed of multiple subunits, including the catalytic core enzyme and additional regulatory subunits
RNA polymerase moves along the DNA template, adding nucleotides to the growing RNA chain
Can be targeted by transcriptional regulators to modulate gene expression

Transcriptional Elongation Rates

Measure of how quickly RNA polymerase transcribes the DNA template
Influenced by factors such as:
- RNA polymerase processivity
- Presence of transcriptional elongation factors
- Chromatin structure and accessibility
- Sequence-specific features of the DNA template
Elongation rates can impact gene expression levels and transcriptional regulation

Transcriptional Pausing

Temporary halting of RNA polymerase during transcription
Can occur at specific sequences or structures, such as:
- Pause sites
- Hairpin structures
- Repetitive sequences
Transcriptional pausing can be a regulatory mechanism, allowing for:
- Temporal regulation of gene expression
- Spatial regulation of gene expression
- Co-transcriptional processing of the RNA transcript

Elongation Factors

Proteins that interact with RNA polymerase to modulate transcriptional elongation
Can stimulate or inhibit transcriptional elongation, depending on the factor
Examples of elongation factors include:
- NusA (stimulates elongation)
- NusG (stimulates elongation)
- GreA and GreB (stimulate elongation and cleavage of backtracked RNA)
- Mfd (stimulates transcriptional proofreading and repair)

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Description

This quiz covers the regulation of transcription, including the formation of the initiation complex, RNA polymerase, transcriptional elongation rates, and transcriptional pausing. It also explores the role of elongation factors in modulating transcriptional elongation.