transcription II- lecture 26

Eukaryotic transcription

Occurs in nucleus, requires multiple transcription factors

Prokaryotic transcription

Occurs in cytoplasm, coupled with translation, simpler

RNA polymerase I

Synthesizes rRNA (28S, 18S, 5.8S)

RNA polymerase II

Synthesizes mRNA, snRNA, miRNA

RNA polymerase III

Synthesizes tRNA, 5S rRNA

TATA box

Promoter element at -25, binds TBP

CAAT box

Promoter element at -75, enhances transcription

GC box

Promoter region binding Sp1 transcription factor

TFIID

Recognizes TATA box via TBP

TFIIB

Recruits RNA pol II

TFIIE

Promoter melting, recruits TFIIH

TFIIF

Stabilizes RNA pol II-TFIIB complex

TFIIH

Helicase (unwinds DNA) + kinase (phosphorylates CTD of Pol II)

5’ capping

Addition of 7-methylguanosine for mRNA stability

Splicing

Removes introns, joins exons via spliceosome

3’ polyadenylation

Addition of poly-A tail for stability and translation

RNA processing

Includes capping, splicing, polyadenylation

Rifampin

Inhibits prokaryotic RNA pol (β subunit), blocks initiation

Actinomycin D

Intercalates DNA, blocks elongation

Alpha-amanitin

Inhibits eukaryotic RNA pol II, mushroom toxin

Transcription bubble

Locally unwound DNA region during transcription

General transcription factors

Required for initiation by RNA polymerase II