Question

The PriA/B/CDnaT proteins are required for initiating DNA replication of the positive strand of the PhiX174 phage genome in order make the replicative form (RF). All of these proteins are encoded by E. coli, not the phage.

Question: What is the function of these proteins in E. coli?
a They are used to recognize DNA legions (mutations) and mark them for repair.
b They are used at OriC only under extreme conditions of heavy mutagenesis.
c They are used to re-prime DNA replication at sites of DNA damage (legions).
d They are normally used at OriC to prime DNA synthesis of the leading strand.

Answer 1

PriA/B/CDnaT proteins in E. coli are part of the replisome responsible for DNA replication initiation and are specifically utilized to re-prime DNA replication at sites of DNA damage. These proteins are vital for maintaining genomic integrity and ensuring continuous DNA replication in the presence of DNA lesions.

Step-by-step explanation:

The PriA/B/CDnaT proteins mentioned in the context of PhiX174 phage genome replication in E. coli play an essential role in DNA replication initiation in their bacterial host as well. These proteins are part of the primosome, a protein complex necessary for initiating DNA synthesis at the replication fork, especially when the replication machinery encounters damages on the DNA, such as those induced by UV light or other mutagenic factors. Specifically, they are involved in re-priming DNA replication at sites of DNA damage, the process known as DNA repair, rather than being exclusively employed during extreme conditions or solely for marking mutations for repair.

In E. coli, these proteins are part of the replisome's ensemble that reacts to stalled replication forks, enabling the bacteria to maintain genomic integrity despite the presence of DNA lesions. Among the given options, the best choice that describes the function of PriA/B/CDnaT proteins in E. coli is that they are used to re-prime DNA replication at sites of DNA damage (option c). This role is critical for the continuity of replication after encountering DNA lesions that would otherwise halt the replication process.