Role of replicative primase in lesion bypass during DNA replication

Maintenance of genome integrity and stability is fundamental for any form of life. This is complicated as DNA is highly reactive and always under attack from a wide range of endogenous and exogenous sources which can lead to different damages in the DNA. To preserve the integrity of DNA replication, cells hav evolved a variety of DNA repair pathways. DNA damage tolerance mechanisms serve as the last line of defence to rescue the stalled replications forks. TLS, error-prone type of DNA damage tolerance, acts to bypass DNA lesions and allows continuation of DNA replication. Surprisingly majority of archaeal species lack canonical TLS polymerases. This poses a question as to how archaea restart stalled replication in the absence of TLS or lesion repair pathways. This thesis establishes that archaeal replicative primase (PriS/L), a member of the archaeo-eukaryotic primase (AEP) superfamily, possessing both primase and polymerase activities, is able to bypass the most common oxidative damages and highly distorting lesions caused by UV radiation. It has been postulated that archaeal replicative polymerases (Pol B and Pol D family Pols) can bind tightly to the deaminated bases uracil and cause replication fork stalling four bases prior to dU. A specific mechanism for resuming replication of uracil containing DNA by PriS/L is suggested in this thesis. In this thesis, we also reported how the enzymatic activities of archaeal PriS/L are regulated. Here, it is demonstrated that in contrast to archaeal replicative polymerases, single-strand binding proteins (RPA) significantly limit the polymerase activity of PriS/L. The remaining results chapter interrogates the possible interactions between PriS/L and RPA. Finally, the attempts to reconstitute an archaeal CMG complex in vitro, with the aim of shedding light on the role of archaeal replicative primase in replication-specific TLS are described.