Homework SourseWhat steps in the eukaryotic transcription cycle are stimula
What steps in the eukaryotic transcription cycle are stimulated by phosphorylation of the carboxyl terminal (CTD) of the large subunit of RNA polymerase II and beyond?
Check all that apply.
promoter escape
| efficient termination |
| efficient elongation |
| recruitment of factors required for initiation |
| recruitment of factors required for RNA processing |
Solution
promoter escape,efficient elongation and recruitment of factors required for RNA processing
Phosphorylation of the CTD is important for regulation of Pol II activity during the transcription cycle: unphosphorylated Pol II is preferentially recruited into the preinitiation complex (PIC) and then becomes phosphorylated during the transition from initiation to elongation.CTD phosphorylation thus has both stimulatory and inhibitory roles;phosphorylation prior to PIC assembly inhibits initiation,while phosphorylation after PIC assembly stimulates promoter escape and elongation.Phosphorylation occurs primarily on serine 2 and serine 5 of the consensus CTD repeat,with serine 2-phosphorylated Rpb1 being enriched distally from the promoter and serine 5-phosphorylated Rpb1 being enriched at promoter-proximal regions.Hyperphosphorylation of the CTD is also linked to other essential events during mRNA synthesis, including recruitment of mRNA modification enzymes and pre-mRNA splicing factors.
