Practice question

During transition to productive elongation, CDK9 cyclin-dependent kinase of P-TEFb complex and later CDK12 phosphorylate serine two of CTD heptad repeats YSPTSPS, creating high density pattern near three prime end of gene body. Serine2-P CTD recruits histone chaperone FACT, Spt6, chromatin modifier Set2 responsible for H3K36 trimethylation, and cleavage and polyadenylation factors CPSF and CstF for messenger RNA three prime end formation. Exchange from serine five to serine two ensures temporal coupling of elongation, chromatin restoration, and termination. Phosphatase Fcp1 recycles polymerase after termination releasing from DNA.