Abstract
Translesion synthesis (TLS) employs specialized DNA polymerases to bypass replication fork stalling lesions. PrimPol was recently identified as a TLS primase and polymerase involved in DNA damage tolerance. Here, we identify a novel PrimPol binding partner, PolDIP2, and describe how it regulates PrimPol's enzymatic activities. PolDIP2 stimulates the polymerase activity of PrimPol, enhancing both its capacity to bind DNA and the processivity of the catalytic domain. In addition, PolDIP2 stimulates both the efficiency and error-free bypass of 8-oxo-7,8-dihydrodeoxyguanosine (8-oxoG) lesions by PrimPol. We show that PolDIP2 binds to PrimPol's catalytic domain and identify potential binding sites. Finally, we demonstrate that depletion of PolDIP2 in human cells causes a decrease in replication fork rates, similar to that observed in PrimPol−/− cells. However, depletion of PolDIP2 in PrimPol−/− cells does not produce a further decrease in replication fork rates. Together, these findings establish that PolDIP2 can regulate the TLS polymerase and primer extension activities of PrimPol, further enhancing our understanding of the roles of PolDIP2 and PrimPol in eukaryotic DNA damage tolerance.
Highlights
IntroductionThe replicative polymerases (Pols) ␣, ␦ and ⑀ are primarily responsible for bulk DNA replication
In eukaryotes, the replicative polymerases (Pols) ␣, ␦ and ⑀ are primarily responsible for bulk DNA replication
Further studies suggested that RPA and mtSSB regulate PrimPol’s enzymatic activities and revealed that, unlike canonical translesion synthesis (TLS) polymerases, PrimPol is not stimulated by the presence of PCNA in vitro (13)
Summary
The replicative polymerases (Pols) ␣, ␦ and ⑀ are primarily responsible for bulk DNA replication. These enzymes, which duplicate DNA with extremely high efficiency and accuracy, are prone to stalling upon encountering helix-distorting DNA lesions generated by DNA damage (1). A number of distinct replication restart mechanisms exist in order to permit continued replication in the presence of damage. These include the firing of dormant origins downstream of the damage, the generation of new Okazaki fragments on the lagging strand or repriming on the leading strand, the use of an alternative sister template to bypass the damage via homologous recombination, and direct synthesis past the damage through translesion synthesis (TLS) (2–4). Archaeal replicative primases are known to display TLS activity (6), whilst most eukaryotes possess a specialized primase-polymerase (PrimPol) that plays roles in TLS and re-priming (7)
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