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CRYSTAL STRUCTURE OF THE CATALYTIC CORE OF HUMAN DNA POLYMERASE ALPHA IN TERNARY COMPLEX WITH AN DNA-PRIMED DNA TEMPLATE AND DCTP
Structural highlights
FunctionDPOLA_HUMAN Plays an essential role in the initiation of DNA replication. During the S phase of the cell cycle, the DNA polymerase alpha complex (composed of a catalytic subunit POLA1/p180, a regulatory subunit POLA2/p70 and two primase subunits PRIM1/p49 and PRIM2/p58) is recruited to DNA at the replicative forks via direct interactions with MCM10 and WDHD1. The primase subunit of the polymerase alpha complex initiates DNA synthesis by oligomerising short RNA primers on both leading and lagging strands. These primers are initially extended by the polymerase alpha catalytic subunit and subsequently transferred to polymerase delta and polymerase epsilon for processive synthesis on the lagging and leading strand, respectively. The reason this transfer occurs is because the polymerase alpha has limited processivity and lacks intrinsic 3' exonuclease activity for proofreading error, and therefore is not well suited for replicating long complexes.[1] Publication Abstract from PubMedDNA 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. See AlsoReferences
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