Transcriptional Regulation of Gene Expression in Eukaryotes

This set of flashcards covers essential concepts from a lecture on transcriptional regulation of gene expression in eukaryotes, focusing on mechanisms of transcription initiation, regulation by transcription factors, splicing, and the impact of mRNA stability and translation processes.

What is required to initiate transcription in eukaryotes?

The entire transcription factor (TF) complex must be assembled on the promoter at the transcription start site.

What role does TF2B play in transcription initiation?

TF2B helps generate single stranded template DNA by strand separation, attracting RNA polymerase II.

Which general transcription factors accompany RNA polymerase II during initiation?

TF2E and TF2F accompany RNA polymerase II during the initiation stage of transcription.

How does the stability of the transcription initiation complex affect RNA polymerase functionality?

The stability determines if RNA polymerase can recruit another RNA polymerase or if the complex disassembles.

What can regulatory proteins do in relation to transcription?

Regulatory proteins bind to DNA sequences and influence the frequency and stability of transcription initiation.

Where are regulatory binding sites typically located in relation to the transcription start site?

They are often located five prime to the transcription start site.

How can DNA bending affect transcription regulation?

DNA bending allows transcription factors bound upstream to interact with the transcription initiation complex at the promoter.

What is the significance of binding sites for activators and repressors?

The ratio of activators to repressors affects transcription levels; more activators increase and more repressors decrease transcription.

What is direct competition in the context of transcription factors?

Two proteins competing for the same binding site cannot bind simultaneously.

How do protein abundance and affinity impact transcription regulation?

Relative abundance determines binding frequency, while affinity affects how long a protein stays bound to its site.

What is alternative splicing?

Alternative splicing allows different mRNA variants to be produced from the same primary transcript.

What is the role of splicing factors?

Splicing factors recognize specific sequences and can influence which exons are included or excluded during splicing.

How do regulatory proteins influence splicing?

They can obscure donor or acceptor sites, affecting which exons are spliced together.

What is the importance of the polyadenylation signal in eukaryotic mRNA?

The polyadenylation signal directs the addition of a poly A tail to the mRNA, influencing its stability.

What is the consequence of alternative transcription start sites?

Different transcription start sites lead to variations in the 5' end of mRNA, potentially altering protein function.

What happens to an mRNA that is not translated?

It may be degraded or kept in the nucleus until needed.

How does the iron response factor (IRF) regulate ferritin production?

The IRF binds to the ferritin mRNA when iron levels are low to block translation.

What does transferrin do, and how is it regulated?

Transferrin is an iron transport protein regulated by IRF; when iron is low, IRF binds and stabilizes its mRNA.

What is the difference in the effects of IRF binding on ferritin and transferrin mRNAs?

IRF binding to ferritin blocks translation; binding to transferrin stabilizes the mRNA, promoting translation.

What allows RNA binding proteins to protect mRNA from degradation?

When bound, RNA binding proteins create a barrier that prevents exonucleases from accessing and degrading the mRNA.

What is the general function of a poly A tail in mRNA?

It increases mRNA stability and protects it from degradation.

How can secondary structures in mRNA influence translation?

They can block ribosomal access to the start codon, inhibiting translation.

What is the role of RNA polymerase during transcription?

RNA polymerase synthesizes RNA by transcribing the DNA template strand.

What does the transcription initiation complex include?

It includes RNA polymerase and various transcription factors assembled at the promoter.

How does transcription termination differ in eukaryotes compared to prokaryotes?

Eukaryotic transcription termination is often less precise and requires specific signals like polyadenylation.

What is the significance of the 7-methylguanylate (m7G) cap?

The m7G cap protects mRNA from degradation and is crucial for ribosome recognition during translation.

What can happen if splicing factors are absent or not functional?

Inappropriate splicing patterns can lead to non-functional proteins or disrupt normal gene expression.

What is the effect of exonucleases on mRNA?

Exonucleases degrade mRNA from the 3' end, leading to reduced stability and eventual degradation.

What is the purpose of alternative splicing?

To produce multiple proteins from a single gene by combining different exons in various ways.

How do mRNA-binding proteins influence gene expression?

They can regulate the stability and translation of mRNA transcripts based on their binding.

What happens during the splicing process?

Introns are removed and exons are joined together to form a continuous mRNA sequence.

Why is post-transcriptional regulation important?

It allows the cell to respond dynamically to environmental changes without altering transcription.

What is a transcription factor?

A protein that helps regulate the transcription of specific genes by binding to nearby DNA.

How can the abundance of a protein affect gene expression?

Higher abundance can enhance transcription or translation, whereas low abundance can reduce expression.

What is RNA stability?

The length of time an mRNA molecule remains intact and available for translation in the cell.

How can changes in cellular conditions affect transcription factor activity?

Changes can influence the binding affinities and specificities of transcription factors, altering gene expression.

What is the impact of multiple transcription start sites on gene expression?

They can lead to production of different protein isoforms with varied functions from the same gene.

What effect does the cleavage of the mRNA have on gene expression?

Cleavage of the mRNA at specific polyadenylation signals determines the final structure and stability of the mRNA.

In what contexts is post-transcriptional regulation particularly critical?

In processes like embryonic development, where precise control over gene expression is vital.

What is the primary role of the spliceosome?

To facilitate the removal of introns and the joining of exons in pre-mRNA.

What does it mean for a gene to be regulated at the level of translation?

The frequency and efficiency of translation initiation can be modified by factors such as RNA binding proteins.

What happens to an mRNA molecule when it is degraded?

Once degraded, it can no longer be translated into protein, and the cell must make new transcripts if needed.

What is the significance of the iron response element (IRE) in mRNA regulation?

The IRE is a sequence where regulatory proteins bind to modulate translation based on iron availability.

How do cells adapt their gene expression in response to environmental signals?

They use various mechanisms of transcriptional and post-transcriptional regulation to adjust protein production.