Transcriptional and Post-Transcriptional Gene Regulation

Vocabulary flashcards covering key terms in transcriptional and post-transcriptional gene regulation.

Differential gene expression

Selective activation or repression of genes that produces different cell types and tissues from an identical genome.

Promoter

DNA sequence immediately upstream of a gene that binds transcription machinery and marks the transcription start site.

TATA box

Conserved AT-rich element within many promoters recognized by transcription factors to position RNA polymerase II.

Transcriptional unit

Portion of a gene that is copied into an RNA molecule during transcription.

RNA polymerase II

Eukaryotic enzyme that synthesizes messenger RNA (mRNA) in a 5′→3′ direction.

General transcription factors (GTFs)

Proteins that assemble at the promoter with RNA Pol II and produce a low basal level of transcription.

Enhancer

Distal DNA regulatory element; binding site for activators that stimulate high transcription by looping to the promoter.

Transcriptional activator

DNA-binding protein that attaches to an enhancer and recruits mediator/RNA Pol II to increase transcription rate.

Transcription bubble

Locally unwound region of DNA where RNA polymerase elongates the RNA transcript.

Rho-independent termination

Prokaryotic termination mechanism in which a GC hairpin followed by poly-U in RNA causes polymerase release.

Rho-dependent termination

Prokaryotic termination mechanism where Rho helicase binds the RNA and dislodges RNA polymerase from DNA.

Cleavage and polyadenylation specific factor (CPSF)

Eukaryotic protein that recognizes the poly-A signal, cleaves pre-mRNA, adds a poly(A) tail, and ends transcription.

5′ Cap

7-methylguanosine triphosphate added to the 5′ end of eukaryotic mRNA; protects RNA and serves as ribosome binding site.

Poly(A) tail

String of ~50–250 adenines added to the 3′ end of mRNA that increases stability and translational efficiency.

Spliceosome

Large complex of snRNAs and proteins that removes introns and ligates exons during mRNA splicing.

snRNA

Small nuclear RNA molecule that forms part of the spliceosome and recognizes splice sites.

snRNP

Complex of snRNA with proteins (small ribonucleoprotein) that constitutes spliceosome subunits.

Intron

Non-coding sequence in pre-mRNA that is removed during splicing.

Exon

Sequence that remains in mature mRNA; may encode protein or reside in untranslated regions.

Open reading frame (ORF)

Continuous codon sequence between start and stop codons that is translated into protein.

5′ Untranslated region (5′-UTR)

mRNA segment upstream of the start codon that regulates ribosome binding and mRNA stability.

3′ Untranslated region (3′-UTR)

mRNA segment downstream of the stop codon that influences mRNA stability and translational efficiency.

Shine-Dalgarno sequence

Prokaryotic ribosome binding site located in the 5′-UTR that aligns the start codon with the ribosome.

Kozak box

Eukaryotic consensus sequence surrounding the start codon that promotes accurate translation initiation.

Alternative splicing

Process that joins exons in different combinations to produce multiple mRNAs and protein isoforms from one gene.

RNA interference (RNAi)

Post-transcriptional silencing pathway mediated by small RNAs that degrade or inhibit target mRNAs.

MicroRNA (miRNA)

Endogenous ~22-nt RNA that guides RISC to complementary mRNAs to repress translation or induce decay.

Small interfering RNA (siRNA)

Double-stranded RNA, often from foreign origin, that triggers sequence-specific degradation of complementary mRNA.

Dicer

RNase III enzyme that processes miRNA/siRNA precursors into 21–23 bp double-stranded RNAs.

RISC (RNA-induced silencing complex)

Protein complex that incorporates a single strand of miRNA/siRNA and targets complementary mRNA for repression.

Promoter strength

Qualitative measure of how efficiently a promoter initiates transcription; strong promoters initiate rapidly, weak promoters slowly.