HMG - Week 13 Qs

This set of vocabulary flashcards covers the mechanisms of eukaryotic gene expression regulation including transcriptional control, chromatin remodeling, DNA methylation, and post-transcriptional RNA processing.

Transcriptional Control

The level of regulation that determines whether a gene is transcribed into RNA, controlled by promoters, enhancers, transcription factors, chromatin structure, and DNA methylation.

RNA Processing and Transport

A level of control that converts pre-mRNA into mature mRNA through 5' capping, splicing, polyadenylation, and export from the nucleus.

Translational Control

A regulatory level that determines how efficiently mRNA is translated into protein, influenced by mRNA stability and poly(A) tail length.

mRNA Degradation

The step in regulation that determines the lifespan of an mRNA molecule before it is destroyed.

Protein Processing

The stage in expression where proteins may require folding, cleavage, or chemical modification to become functional.

Protein Degradation

The selective destruction of proteins when they are no longer needed by the cell.

Activator Proteins

Regulatory proteins that bind to promoter and enhancer elements to recruit chromatin-remodelling proteins and RNA polymerase II to increase transcription initiation.

Repressor Proteins

Regulatory proteins that bind DNA sequences to prevent transcription factor binding and recruit chromatin-condensing proteins to block RNA polymerase access.

DNA Looping

A process where DNA bends to allow enhancers, which may be thousands of base pairs away, to physically interact with transcription machinery at the promoter.

Chromatin Remodelling

The process of changing the accessibility of DNA to transcription machinery by altering the organization of nucleosomes.

Histone Acetyltransferases (HATs)

Enzymes that add acetyl groups to lysine residues on histones, reducing their positive charge to loosen DNA-histone interactions and open chromatin.

Histone Deacetylases (HDACs)

Enzymes that remove acetyl groups from histones, causing chromatin condensation and restricting promoter access, leading to decreased transcription.

ATP-Dependent Chromatin Remodelling

A process involving complexes that use ATP to reposition nucleosomes and expose promoter sequences.

DNA Methylation

The addition of a methyl group ($-\text{CH}_3$) to cytosine bases, usually at CpG sites, which prevents transcription factor binding and promotes chromatin condensation.

Hypomethylation

A state of low DNA methylation where chromatin remains open, allowing transcription factors to bind and increase gene expression.

Hypermethylation

A state of high DNA methylation where chromatin becomes condensed, leading to a decrease in transcription.

Alternative Splicing

A mechanism where different combinations of exons from a single pre-mRNA are joined together to produce multiple mature mRNAs and different protein isoforms.

Alternative Polyadenylation

A process where different poly(A) sites are used, changing mRNA stability, translation efficiency, and regulatory sequences in the 3' UTR.

Poly(A) Tail

A chain of adenine nucleotides at the 3' end of mRNA; a long tail increases stability and translation, while a short tail promotes degradation.

miRNAs (microRNAs)

Small regulatory RNAs that silence genes post-transcriptionally by guiding the RISC complex to complementary mRNA for cleavage or translational blocking.

siRNAs (small interfering RNAs)

Small regulatory RNAs involved in RNA interference (RNAi) that target complementary mRNA for degradation or inhibition.

Dicer

The enzyme responsible for processing double-stranded RNA into small fragments like miRNAs and siRNAs.

RISC (RNA-Induced Silencing Complex)

A complex that uses small RNA fragments as guides to target complementary mRNA for silencing.