L14: Gene Expression 2 Flashcards
(49 cards)
What is the primary function of RNA polymerase in gene expression?
RNA polymerase transcribes DNA into RNA, initiating the first step of gene expression
What role does the core promoter play in transcription?
The core promoter contains sequences necessary for RNA polymerase binding, which initiates transcription
How do enhancer sequences affect gene expression?
Enhancer sequences increase the transcription rate by binding transcription factors that enhance RNA polymerase activity
What is the TATA box, and where is it located?
The TATA box is a DNA sequence within the core promoter, around 25-30 base pairs upstream of the transcription start site, and helps position RNA polymerase
- Only found in 24% of genes - regulated by alternative promoter sequences or mechanisms
Describe the role of transcription factor IID (TFIID)
TFIID recognizes the core promoter and recruits RNA polymerase and other transcription factors to initiate transcription
What are the three types of RNA polymerase in eukaryotes, and their functions?
- RNA polymerase I transcribes rRNA genes
- RNA polymerase II transcribes mRNA
- RNA polymerase III transcribes tRNA and other small RNAs
How does chromatin structure impact transcription?
Chromatin structure, including DNA methylation and histone modifications, can repress or permit access to DNA for transcription
What is the function of the C-terminal domain (CTD) of RNA polymerase II?
The CTD becomes phosphorylated to recruit factors needed for mRNA processing, such as capping, splicing, and polyadenylation
How do transcription factors recognize specific DNA sequences?
Transcription factors bind to specific DNA motifs through their DNA-binding domains, enabling targeted gene regulation
What is alternative splicing, and why is it important?
Alternative splicing is the process by which different mRNA variants are produced from a single gene, allowing diverse protein functions
What are non-coding RNAs, and what roles do they play?
Non-coding RNAs do not encode proteins but are involved in gene regulation, through RNA interference and chromatin remodeling
Why is the assembly of the transcription initiation complex tightly regulated?
Tight regulation ensures genes are transcribed only when needed, preventing inappropriate gene expression that could harm the cell
What is the function of transcription factor II H (TFIIH)?
TFIIH has helicase activity that unwinds DNA, allowing RNA polymerase to access the DNA template for transcription
What is the significance of the TATA-binding protein (TBP) within TFIID?
TBP specifically binds to the TATA box, bending DNA to facilitate the recruitment of additional transcription machinery
How do silencer sequences function in gene regulation?
- Silencer sequences are DNA regions that repress transcription, often located upstream or downstream of the regulated gene
- Silencers bind repressors to decrease gene expression by inhibiting transcription initiation
What is the holoenzyme in the context of transcription?
The holoenzyme is the fully assembled complex of RNA polymerase and its associated factors needed to initiate transcription
How do proximal promoter elements influence transcription?
Proximal promoter elements, located near the core promoter, bind transcription factors that modulate the rate of transcription initiation
What is the role of the mediator complex in transcription?
The mediator complex bridges transcription factors bound to enhancers with the RNA polymerase machinery at the promoter, facilitating transcription
Describe the function of small inhibitory RNAs (siRNAs) in gene regulation
siRNAs bind to target mRNAs to promote degradation or prevent translation, acting as a post-transcriptional regulatory mechanism
What is chromatin remodeling, and why is it necessary for transcription?
Chromatin remodeling adjusts nucleosome positioning to expose or conceal DNA sequences, making transcription sites accessible to transcription machinery like RNA polymerase
What are histone modifications, and how do they influence gene expression?
Histone modifications, such as acetylation and methylation, alter chromatin structure, either promoting or repressing transcriptional activity
Explain the concept of transcriptional silencing through DNA methylation
DNA methylation involves adding methyl groups to cytosine bases, typically silencing gene expression by blocking transcription factor binding or recruiting proteins that compact chromatin
What is the significance of enhancer-promoter looping in gene expression?
Enhancer-promoter looping brings distal enhancers into proximity with promoters, allowing enhancers to increase transcription of distant genes
Define alternative polyadenylation and its impact on mRNA
Alternative polyadenylation generates mRNA variants with different 3’ ends, influencing mRNA stability, localization, and translation efficiency
