Ch. 9: Post-Transcriptional Control of Gene Expression

These flashcards cover key concepts around post-transcriptional gene control, including RNA processing, regulation, and various involved mechanisms.

What is the most significant control for gene expression?

It occurs at the level of gene transcription, particularly the rates of transcription initiation.

What happens to primary RNA transcripts before they are functional?

They undergo maturation in the nucleus, including modifications like capping, splicing, and polyadenylation.

What is post-transcriptional gene control?

It refers to mechanisms that regulate gene expression following transcription.

What are Heterogeneous nuclear RNAs (hnRNA)?

They include pre-mRNAs and RNA-processing intermediates containing one or more introns.

What is the role of small nuclear RNAs (snRNAs) in RNA processing?

They function in the removal of introns from pre-mRNAs by RNA splicing.

What is the difference between miRNA and siRNA?

miRNA inhibits translation with imperfect base pairing, while siRNA leads to cleavage of target mRNA with perfect base pairing.

What does it mean to say that mRNA is deadenylated?

It refers to the removal of the poly(A) tail, which can lead to mRNA degradation.

What is the main role of Exosomes?

They degrade improperly processed or unneeded RNA transcripts.

What is the significance of the IRE-BP in gene regulation?

IRE-BP regulates translation initiation and degradation of mRNAs based on intracellular iron levels.

What key modifications occur to pre-rRNA in the nucleolus?

Cleavage reactions, 2'-O-methylations, and conversion to pseudouridine.

What is alternative splicing?

It is a process that allows multiple mRNA variants to be produced from a single gene by including or excluding certain exons.

What is the function of the Nuclear Pore Complex (NPC)?

It regulates the export of mature RNAs and the import of nuclear proteins.

What role do signaling pathways like mTOR play in gene expression?

They regulate global translation initiation rates in response to growth factors and nutrient levels.

How does RNA editing occur?

It can involve insertion, deletion, or modification of nucleotides in the RNA sequence post-transcriptionally.

What are the two main types of pathways for RNA degradation?

Deadenylation-dependent decay and deadenylation-independent decay.

What is the mechanism by which cells recognize and destroy faulty mRNAs?

Nonsense-mediated decay targets mRNAs if they have premature termination codons and have not been dislodged by ribosome translation.

What are Cajal bodies and their function?

They are sites for snRNA modification, involved in the 2'-O-methylation and pseudouridylation of RNAs.

What effect do AG-rich sequences have on mRNA stability?

They typically decrease mRNA stability and can promote degradation.

How does the SR protein Npl3 function in mRNP export?

Npl3 is phosphorylated in the cytoplasm and helps recruit mRNA export factors.

What is the function of snoRNAs?

They guide site-specific modifications of rRNA, such as methylation and pseudouridylation.

Why is alternative splicing important in eukaryotes?

It greatly expands the diversity of proteins that can be produced from a single gene.

What happens to pre-tRNAs during processing?

They undergo 5' leader removal, and may include intron splicing, as well as various nucleotide modifications.