Question

What would happen if the serines in the C-Terminal Domain of RNA POL II were mutated to alanines?

Answer 1

C-Terminal domain of the RNA Polymerase-II contain heptad repeats comprises of Serine residues. These Serine residues are essential for the Phosphorylation. This Phosphorylation activates gene transcription. If the Serine in C-Terminal Domain of RNA POL II is mutated to alanine, no phosphorylation takes place, intern there is no transcription.

As Serine contain Hydroxyl group (-OH) it can phosphorylated by ester bond. But Alanine does not possess -OH group and no phosphorylation takes place