Which subunits of RNA polymerase (RNAP) are homologous to a1 and a2 in RNAP II?

The correct answer relates to the subunits of RNA polymerase and their structural and functional similarities. In eukaryotic RNA polymerase II, the subunits Rpb3 and Rpb11 are homologous to the subunits a1 and a2 found in bacterial RNA polymerase.

To understand this better, it's essential to know that RNA polymerase is a multi-subunit enzyme responsible for synthesizing RNA from a DNA template. In E. coli, the core RNA polymerase consists of two alpha subunits (a1 and a2), which play crucial roles in enzyme assembly and ensuring the stability of the complex.

Similarly, in RNA polymerase II, Rpb3 and Rpb11 serve analogous functions as part of the enzyme's core. They are involved in forming interactions at the interface of the enzyme subunits, helping to stabilize the structure and enabling proper functionality during transcription. This evolutionary conservation suggests that Rpb3 and Rpb11 have retained some structural and functional roles akin to those of the bacterial a subunits.

Understanding the functional architecture of these polymerases highlights the evolutionary relationships between different organisms and the conservation of essential biological processes like transcription. This context is integral for grasping why Rpb3 and Rpb11 are the