{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,10,23]],"date-time":"2026-10-23T21:19:32Z","timestamp":1792790372862,"version":"4.5.0"},"posted":{"date-parts":[[2026,10,2]]},"group-title":"Biochemistry","reference-count":42,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T00:00:00Z","timestamp":1790899200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"award":["R01 GM129245"],"award-info":[{"award-number":["R01 GM129245"]}],"id":[{"id":"https:\/\/ror.org\/04q48ey07","id-type":"ROR","asserted-by":"publisher"}]},{"award":["R35 GM144121"],"award-info":[{"award-number":["R35 GM144121"]}],"id":[{"id":"https:\/\/ror.org\/04q48ey07","id-type":"ROR","asserted-by":"publisher"}]},{"award":["Emerging Pathogens Initiative"],"award-info":[{"award-number":["Emerging Pathogens Initiative"]}],"id":[{"id":"https:\/\/ror.org\/006w34k90","id-type":"ROR","asserted-by":"publisher"}]},{"award":["Investigator Program"],"award-info":[{"award-number":["Investigator Program"]}],"id":[{"id":"https:\/\/ror.org\/006w34k90","id-type":"ROR","asserted-by":"publisher"}]},{"name":"U.S. National Science Foundation","award":["DBI 1920374"],"award-info":[{"award-number":["DBI 1920374"]}],"id":[{"id":"https:\/\/ror.org\/021nxhr62","id-type":"ROR","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,10,1]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                <jats:p>\n                  Viruses that infect bacteria, termed bacteriophages or phages, typically encode their own DNA replication machinery that rapidly generates many copies of the phage genomic DNA in an infected cell. Nucleus-forming phages of the chimallivirus family possess a distinctive repertoire of predicted DNA replication proteins, with two proteins annotated as DNA polymerases plus a DnaB-like replicative helicase, but lacking an identified primase or sliding clamp protein. Here, we demonstrate that in the\n                  <jats:italic>Pseudomonas aeruginosa<\/jats:italic>\n                  -infecting chimallivirus PhiKZ, the core DNA polymerase comprises a stable 1:1 complex of two DNA polymerase subunits, termed DNAP\n                  <jats:sup>N<\/jats:sup>\n                  and DNAP\n                  <jats:sup>C<\/jats:sup>\n                  . A 2.1 \u00c5 resolution cryoelectron microscopy structure of this core complex reveals homology to other phage and bacterial B-family DNA polymerases. Next, we identify a direct but transient interaction between the core DNA polymerase complex and a third protein termed Rhc, which possesses an N-terminal RNase H domain and a C-terminal domain related to DNA sliding clamp proteins. Cryoelectron microscopy structures of a stabilized DNA polymerase-Rhc complex, and of this complex bound to a primer-template DNA, reveal a single Rhc subunit that cooperates with the DNA polymerase thumb domain to bind double-stranded DNA emerging from the DNA polymerase active site. While the Rhc RNase H domain is not resolved in our structures, this domain is situated such that it could degrade RNA associated with an incoming template DNA strand.\n                  <jats:italic>In vitro<\/jats:italic>\n                  primer-extension assays show that Rhc strongly boosts DNA polymerase activity, and that this boost relies on the Rhc-DNA polymerase interface we observe in our structures. Overall, our findings reveal a distinctive chimallivirus-specific DNA replication machine with an integrated DNA-binding subunit related to sliding clamp proteins, and a flexibly-linked RNase H domain.\n                <\/jats:p>","DOI":"10.64898\/2026.09.30.755723","type":"posted-content","created":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T09:35:13Z","timestamp":1790933713000},"source":"Crossref","is-referenced-by-count":0,"title":["A bacteriophage split DNA polymerase incorporates a sliding clamp-derived processivity subunit"],"prefix":"10.64898","author":[{"given":"Dwaipayan","family":"Basu","sequence":"first","affiliation":[{"name":"Department of Biochemistry and Molecular Biophysics, University of California San Diego, La Jolla CA 92093"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ryan K.","family":"Min","sequence":"additional","affiliation":[{"name":"Department of Molecular Biology, University of California San Diego, La Jolla CA 92093"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Koe","family":"Inlow","sequence":"additional","affiliation":[{"name":"Department of Molecular Biology, University of California San Diego, La Jolla CA 92093"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joe","family":"Pogliano","sequence":"additional","affiliation":[{"name":"Department of Molecular Biology, University of California San Diego, La Jolla CA 92093"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4677-9809","authenticated-orcid":false,"given":"Elizabeth","family":"Villa","sequence":"additional","affiliation":[{"name":"Department of Molecular Biology, University of California San Diego, La Jolla CA 92093"},{"name":"Howard Hughes Medical Institute, University of California San Diego, La Jolla, CA 92093"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5854-2388","authenticated-orcid":false,"given":"Kevin D.","family":"Corbett","sequence":"additional","affiliation":[{"name":"Department of Molecular Biology, University of California San Diego, La Jolla CA 92093"},{"name":"Department of Cellular & Molecular Medicine, University of California San Diego, La Jolla CA 92093"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026100705100938000_2026.09.30.755723v1.1","doi-asserted-by":"publisher","DOI":"10.1038\/s41586-020-2007-4"},{"key":"2026100705100938000_2026.09.30.755723v1.2","doi-asserted-by":"publisher","DOI":"10.1038\/s41467-023-36526-9"},{"key":"2026100705100938000_2026.09.30.755723v1.3","doi-asserted-by":"publisher","DOI":"10.1038\/s41586-022-05013-4"},{"key":"2026100705100938000_2026.09.30.755723v1.4","doi-asserted-by":"publisher","DOI":"10.1126\/science.aal2130"},{"key":"2026100705100938000_2026.09.30.755723v1.5","doi-asserted-by":"publisher","DOI":"10.1016\/j.chom.2025.03.005"},{"key":"2026100705100938000_2026.09.30.755723v1.6","first-page":"48","article-title":"A jumbo phage that forms a nucleus-like structure evades CRISPR-Cas DNA targeting but is vulnerable to type III RNA-based immunity","volume":"5","year":"2020","journal-title":"Nat. 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