title: DNA Topology and the Initiation of Virus DNA Packaging.
abstract: During progeny assembly, viruses selectively package virion genomes from a nucleic acid pool that includes host nucleic acids. For large dsDNA viruses, including tailed bacteriophages and herpesviruses, immature viral DNA is recognized and translocated into a preformed icosahedral shell, the prohead. Recognition involves specific interactions between the viral packaging enzyme, terminase, and viral DNA recognition sites. Generally, viral DNA is recognized by terminase's small subunit (TerS). The large terminase subunit (TerL) contains translocation ATPase and endonuclease domains. In phage lambda, TerS binds a sequence repeated three times in cosB, the recognition site. TerS binding to cosB positions TerL to cut the concatemeric DNA at the adjacent nicking site, cosN. TerL introduces staggered nicks in cosN, generating twelve bp cohesive ends. Terminase separates the cohesive ends and remains bound to the cosB-containing end, in a nucleoprotein structure called Complex I. Complex I docks on the prohead's portal vertex and translocation ensues. DNA topology plays a role in the TerSλ-cosBλ interaction. Here we show that a site, I2, located between cosN and cosB, is critically important for an early DNA packaging step. I2 contains a complex static bend. I2 mutations block DNA packaging. I2 mutant DNA is cut by terminase at cosN in vitro, but in vivo, no cos cleavage is detected, nor is there evidence for Complex I. Models for what packaging step might be blocked by I2 mutations are presented.
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Choon Seok
authors.initials: CS
authors.lastname: Oh
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Jean
authors.initials: J
authors.lastname: Sippy
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Bridget
authors.initials: B
authors.lastname: Charbonneau
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Crow Hutchinson
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Olga Esther
authors.initials: OE
authors.lastname: Mejia-Romero
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Michael
authors.initials: M
authors.lastname: Barton
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Priyal
authors.initials: P
authors.lastname: Patel
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Rachel
authors.initials: R
authors.lastname: Sippy
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Michael
authors.initials: M
authors.lastname: Feiss
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D010582:Bacteriophage lambda / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D042003:DNA Packaging / Q000235:genetics*; D004267:DNA Viruses / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics*; D004706:Endodeoxyribonucleases / Q000378:metabolism; D019065:Virus Assembly / Q000235:genetics*
chemical_list: D004279:DNA, Viral; D004706:Endodeoxyribonucleases; C030894:terminase; D000251:Adenosine Triphosphatases