Yeast Rev1 protein promotes complex formation of DNA polymerase ζ with Pol32 subunit of DNA polymerase δ

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Abstract
Yeast DNA polymerase (Pol) δ, essential for DNA replication, is comprised of 3 subunits, Pol3, Pol31, and Pol32. Of these, the catalytic subunit Pol3 and the second subunit Pol31 are essential, whereas the Pol32 subunit is not essential for DNA replication. Although Pol32 is an integral component of Polδ, it is also required for translesion synthesis (TLS) by Polζ. To begin to decipher the bases of Pol32 involvement in Polζ-mediated TLS, here we examine whether Pol32 physically interacts with Polζ or its associated proteins and provide evidence for the physical interaction of Pol32 with Rev1. Rev1 plays an indispensable structural role in Polζ-mediated TLS and it binds the Rev3 catalytic subunit of Polζ. Here, we show that although Pol32 does not directly bind Polζ, Pol32 can bind the Rev1–Polζ complex through its interaction with Rev1. We find that Pol32 binding has no stimulatory effect on DNA synthesis either by Rev1 in the Rev1–Pol32 complex or by Polζ in the Polζ–Rev1–Pol32 complex, irrespective of whether proliferating cell nuclear antigen has been loaded onto DNA or not. We discuss evidence for the biological significance of Rev1 binding to Pol32 for Polζ function in TLS and suggest a structural role for Rev1 in modulating the binding of Polζ with Pol32 in Polδ stalled at a lesion site.