Good cap/bad cap: how the cap-binding complex determines RNA fate

摘要

Acquisition of the m~7G cap at the 5' ends of RNA polymerase II (Pol II) transcripts is the earliest RNA-processing event, occurring after only ~25 nt of transcription. The cap is a hallmark of successful transcription initiation and protects transcripts from exonucleolytic degradation. The cap is cotranscriptionally bound by the CBC consisting of subunits CBP20 and CBP80. The CBC binds to different classes of transcribed RNA—(pre-)mRNAs, histone mRNAs, small nuclear RNAs (snRNAs), small nucleolar RNAs (snoRNAs) and promoter upstream transcripts (PROMPTs)—and promotes numerous steps in RNA metabolism, such as pre-mRNA splicing'-end processing, intranuclear transport5, mRNA export to the cytoplasm, nonsense-mediated decay and translation.