Helicobacter pylori is the most infectious human pathogen that causes gastritis, peptic ulcers and stomach cancer. H. pylori DNA polymerase I (HpPol I) is found to be essential for the viability of H. pylori, but its intrinsic property and attribution to the H. pylori DNA replication remain unclear. HpPol I contains a 5′→3′ exonuclease (5′‐Exo) and DNA polymerase (Pol) domain, respectively, but lacks a 3′→5′ exonuclease, or error proofreading activity. In this study, we characterized the 5′‐Exo and Pol functions of HpPol I and found that HpPol I is a multifunctional protein displaying DNA nick translation, strand‐displacement synthesis, RNase H‐like, structure‐specific endonuclease and exonuclease activities. In the in vitro DNA replication assay, we further demonstrated that the 5′‐Exo and Pol domains of HpPol I can cooperate to fill in the DNA gap, remove the unwanted RNA primer from a RNA/DNA hybrid and create a ligatable nick for the DNA ligase A of H. pylori to restore the normal duplex DNA. Altogether, our study suggests that the two catalytic domains of HpPol I may synergistically play an important role in the maturation of Okazaki fragments during the lagging‐strand DNA synthesis in H. pylori. Like the functions of DNA polymerase I in Escherichia coli, HpPol I may involve in both DNA replication and repair in H. pylori.

中文翻译：

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多功能DNA聚合酶I参与幽门螺杆菌的滞链DNA合成过程中冈崎片段的成熟

幽门螺杆菌是引起人胃炎，消化性溃疡和胃癌的最具传染性的人类病原体。发现幽门螺杆菌DNA聚合酶I（HpPol I）对于幽门螺杆菌的生存是必不可少的，但是其内在性质和归因于幽门螺杆菌DNA复制仍然不清楚。HpPol I分别包含5'→3'核酸外切酶（5'-Exo）和DNA聚合酶（Pol）结构域，但缺乏3'→5'核酸外切酶或错误校正功能。在这项研究中，我们对HpPol I的5'-Exo和Pol功能进行了表征，发现HpPol I是一种多功能蛋白质，具有DNA缺口翻译，链置换合成，RNase H样，结构特异性核酸内切酶和核酸外切酶活性。在体外DNA复制测定，我们进一步证明了HpPol I的5'-Exo和Pol结构域可以合作填补DNA缺口，从RNA / DNA杂合物中去除不需要的RNA引物，并为DNA连接酶A产生可连接的缺口幽门螺杆菌恢复正常的双链DNA。总而言之，我们的研究表明，HpPol I的两个催化结构域可能在幽门螺杆菌的滞后链DNA合成过程中在Okazaki片段的成熟中起着重要作用。像大肠杆菌中DNA聚合酶I的功能一样，HpPol I可能参与幽门螺杆菌的DNA复制和修复。