SCH2226 Human Molecular Genetics - Lecture 10 Flashcards

This flashcard set covers the key concepts of eukaryotic gene expression regulation, including chromatin remodeling, RNA interference mechanisms, and post-transcriptional processing as presented in Lecture 10 of Human Molecular Genetics.

Operon

A genetic unit consisting of a promoter, an operator, and multiple genes all under the control of that single promoter and operator.

C. elegans Operons

Genetic structures in nematodes where about $15\%$ of genes are in operons ranging from $2-8$ genes in size, containing typical eukaryotic introns.

Trans-splicing

A process in nematode operon resolution where polygenic pre-mRNA is processed into monocistronic mRNAs involving a Spliced leader (SL RNA).

Chromatin modelling (remodelling)

The process of altering chromatin structure near the promoter to allow activation of eukaryotic genes, caused by acetylating and deacetylating enzymes.

Histone acetyl transferases (HATs)

Multi-protein complexes that acetylate lysines in the amino-terminus of core histones, pushing them apart and changing $30\text{-nm}$ chromatin to $10\text{-nm}$ fiber.

Histone deacetylases (HDACs)

Enzymes that remove acetyl groups from histones, causing the reform of $30\text{-nm}$ chromatin and making the promoter less accessible.

Nucleosome remodeling complexes

ATP-dependent multiprotein complexes that alter nucleosome positions on chromatin in response to activators binding to DNA.

Combinatorial Gene Regulation

A mechanism where eukaryotic gene expression is controlled by specific combinations of regulatory proteins binding to enhancers and promoters.

Steroid Hormone Receptor (SHR)

A cytoplasmic receptor that, when bound to a steroid hormone, forms a complex that binds directly to DNA to regulate gene expression.

Alternative Polyadenylation

A post-transcriptional RNA processing option involving the selection of different polyadenylation sites to produce structurally and functionally different proteins.

Differential Splicing

Also known as alternative splicing; a process where different combinations of exons from the same pre-mRNA are joined together.

RNA Interference (RNAi)

A mechanism that inhibits gene expression at the stage of translation or by hindering the transcription of specific genes, also called interfering RNA (iRNA).

Dicer

An ATP-dependent RNase III-like dsRNA-specific ribonuclease that digests double-stranded RNA into uniformly sized small RNAs of $20\text{-}25\,bp$.

siRNA (Small interfering RNA)

Double-stranded RNA fragments of $21\text{-}22\,nt$ with $5'\text{-phosphate}$ termini, $3'\text{-hydroxyl}$ termini, and $2/3\text{-nucleotide}$ $3'$ overhangs.

miRNA (MicroRNA)

Single-stranded RNA fragments of $19\text{-}25\,nt$ encoded by the non-protein coding genome.

RNA-Induced Silencing Complex (RISC)

A large (~$500\text{-kDa}$) RNA-multi protein complex that triggers mRNA degradation in response to siRNA.

Argonaute proteins

The active endonuclease components of an RISC that cleave the target mRNA strand guided by unwound siRNA.

Drosha

An enzyme that cleaves the base hairpin to form pre-miRNA, which is later processed by Dicer.

Protein Kinase R (PKR)

An intracellular kinase activated by dsRNA longer than $30\,nt$ that induces the production of Interferon (IFN) family cytokines.

Antisense Oligonucleotides

Synthetic polymers, usually $15\text{-}20$ nucleotides long, with a $3' \rightarrow 5'$ sequence complementary to the sense sequence of a target mRNA molecule.