Question

1. (3 pts) TFIIH plays several critical roles in transcription initiation. Which of the following will halt transcription earlier in the process? Why? a. a loss of function mutation in the kinase domain b. a loss of function mutation in the helicase domain Grading: 1 pt for correctly indicating which mutation halted transcription earlier in the process. 2 pts for explaining what the function of each activity is and how that explains which acts earlier in the process.

Answer 1

TFIIH is a complex factor having multiple enzyme activity like helicase, kinase , ATPase, DNA repair activity etc.

Kinase domain helps in the phosphorylation of CTD (carboxy terminal domain) of RNA polymerase II. Phosphorylation of CTD helps in the escape of RNA polymerase II from the promoter and begins the transcription.

- RNA poly II УЅР ТС Р repulsion bed ween phosphate os of dua and phosphate ISP of CTD causes. 10 escape of RNA poly I стр Клоще e и from promotor. phosphorylates Cadd Phosphate to these amino acid residue)

Helicase activity promotes the unwinding to open the complex and for that it requires hydrolysis of ATP.

So if mutation occur in kinase domain it will not phosphorylate CTD of RNA polymerase II and transcription will not initiate.

And if mutation occur in helicase domain it will not be able to hydrolyse the ATP and early RNA polymerase II elongation complex will arrest at promoter.