FC0016
RNA polymerase II C terminal domain  -  mRNA maturation factors

Biological function
Unphosphorylated RNAP II CTD is required for initiation of transcription and interacts with a range of general transcription factors. After initiation of transcription, the CTD interacts with kinases (e.g. TFIIH) and is phosphorylated, which ultimately leads to exclusion of initiation factors and formation of the elongation complex. Capping enzymes associate with the phospho-CTD, which also orchestrates the mRNA splicing machinery.

Domain organization/sequence features
The CTD is a heptad amino acid sequence, which is repeated 52 times in mammals and 26 times in yeast.

Structural evidence
The RNAPII CTD is an unstructured region, it is absent from the crystal structures of the complex (e.g. 3h3v).

Biochemical evidence
Phosphorylation status of the CTD determines the stage of transcription. Owing to the lack of CTDs Pol I and III promoters are unable to generate transcripts, which are capable of mRNA processing.

Mechanism category
tethering

Significance
Phosphorylation status of a fuzzy region determines the progress of transcription and ultimately serves as a termination signal via recruiting the splicing machinery. This is achieved by rewiring of the interactions between RNAP and the initiation vs. termination factors.