TLS Online TPP Program

#Question id: 12482


The Rb protein has been called the “master brake” of the cell cycle. How the Rb protein acts as a cell cycle brake?

#Unit 2. Cellular Organization
  1. Rb bound to E2F and function as transcriptional repressors because Rb recruits chromatin-modifying enzymes that promote deacetylation and methylation of specific histone lysines, causing chromatin to assume a condensed, transcriptionally inactive form.
  2. S phase CDKs and mitotic CDKs maintain Rb protein in the phosphorylated state throughout the S, G2, and early M phases.
  3. Rb bound to E2F and promotes ubiquitinylation of E2F and inhibits chromosomal segregation.
  4. Rb bound to E2F and promotes acetylation which prevents unloading of cohesins.
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TLS Online TPP Program

#Question id: 4514

#Unit 3. Fundamental Processes

What is true about coactivators,

A. The coactivators act directly by binding to the DNA

B. The coactivators act indirectly—not by binding to the DNA

C. Are required for essential communication between the activators and the complex composed of Pol II.

D. Are required for essential communication between the and the basal (or general) transcription factors.

TLS Online TPP Program

#Question id: 4515

#Unit 3. Fundamental Processes

Transcription Activators are,

A. Known to facilitate transcription at hundreds of promoters,

B. Specific for a few promoters,

C. Sensitive to the binding of signal molecules,

D. Providing the capacity to activate or deactivate transcription in response to a changing cellular environment.

TLS Online TPP Program

#Question id: 4516

#Unit 3. Fundamental Processes

High mobility group (HMG) proteins

A. are a common type of architectural regulator

B. facilitating the looping of the DNA

C. the binding is relatively very specific

D. are abundant in chromatin and bind to DNA with limited specificity.

TLS Online TPP Program

#Question id: 4517

#Unit 3. Fundamental Processes

Statement: When phosphorylated, CREB binds to CREs near certain genes and acts as a transcription factor, turning on the expression of these genes.

Explanation: I-Regulation can result from phosphorylation of Nuclear transcription factor

II- Activation of a protein kinase in the nucleus that phosphorylates specific DNA-binding proteins and thereby alters their ability to act as transcription factors.

TLS Online TPP Program

#Question id: 4518

#Unit 3. Fundamental Processes

The sequence of transcriptional activation events at a typical Pol II promote

I- Mediator facilitates the binding of TBP (or TFIID) and TFIIB, and the other basal transcription factors and Pol II then bind.

II- Activators bind the DNA.

III-The activators recruit the histone modification/nucleosome remodeling complexes and a coactivator such as Media.

IV- Phosphorylation of the carboxyl-terminal domain (CTD) of Pol II leads to transcription initiation.

TLS Online TPP Program

#Question id: 4519

#Unit 3. Fundamental Processes

Some steroid hormone receptors function in the nucleus as transcription activators, stimulating the transcription of certain genes when a particular steroid hormone signal is present. When the hormone is absent, the receptor proteins revert to a repressor conformation, preventing the formation of PICs. It is an example of;