6as7

Publication Abstract from PubMed

DNA polymerase alpha (Polalpha) plays an important role in genome replication. In a complex with primase, Polalpha synthesizes chimeric RNA-DNA primers necessary for replication of both chromosomal DNA strands. During RNA primer extension with deoxyribonucleotides, Polalpha needs to use double-stranded helical substrates having different structures. Here, we provide a detailed structure-function analysis of human Polalpha's interaction with dNTPs and DNA templates primed with RNA, chimeric RNA-DNA, or DNA. We report the crystal structures of two ternary complexes of the Polalpha catalytic domain containing dCTP, a DNA template, and either a DNA or an RNA primer. Unexpectedly, in the ternary complex with a DNA:DNA duplex and dCTP, the "fingers" subdomain of Polalpha is in the open conformation. Polalpha induces conformational changes in the DNA and hybrid duplexes to produce the universal double helix form. Pre-steady state kinetic studies indicated for both duplex types that chemical catalysis rather than product release is the rate-limiting step. Moreover, human Polalpha extended DNA primers with higher efficiency but lower processivity than it did with RNA and chimeric primers. Polalpha has a substantial propensity to make errors during DNA synthesis, and we observed that its fidelity depends on the type of sugar at the primer 3'-end. A detailed structural comparison of Polalpha with other replicative DNA polymerases disclosed common features and some differences, which may reflect the specialization of each polymerase in genome replication.

Activity and fidelity of human DNA polymerase alpha depend on primer structure.,Baranovskiy AG, Duong VN, Babayeva ND, Zhang Y, Pavlov YI, Anderson KS, Tahirov TH J Biol Chem. 2018 Mar 19. pii: RA117.001074. doi: 10.1074/jbc.RA117.001074. PMID:29555682^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.