RNA Processing If Ser5 of the CTD of RNA PolII cannot be pho

RNA Processing:

If Ser5 of the CTD of RNA PolII cannot be phosphorylated by TFIIH, what effect would this have on RNA processing?

If the sequence AAUAAA is deleted from a gene, what effect would this have on transcription and RNA processing?

Solution

Answer:

The heptad sequence at the CTD \" Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7 \" is conserved and is pertinent for RNA processing. The CTD is reversibly modified by several enzymes.

Phosphorylation of Ser5 by TFIIH kinase ( Kin28 in yeast and CDK7 in metazoans) helps in movement of RNAPII away from the initiation site. failure to phosphorylate Ser5 leads to impairment in the association of m7G RNA capping machinery.

S equence AAUAAA is considered to be a part of signal for cleavage and polyadenylation of appropriate eukaryotic precursor mRNA

deletion of this site decreses the effeciency of adenylation during RNA processing.

and during transcription such trnascripts are unusually longer than than the normal AAUAAA transcripts having inhanced half life.

AAUAAA demarcates the site for cleavge and subsequent polyadenylation, deletion of this site prevents polyadenylation during RNA pocessing.