title: Effect of human immunodeficiency virus type 1 (HIV-1) nucleocapsid protein on HIV-1 reverse transcriptase activity in vitro.
abstract: Conversion of human immunodeficiency virus type 1 (HIV-1) genomic RNA to viral DNA is a requisite step in the virus life cycle. This conversion is catalyzed by reverse transcriptase (RT) associated with a large nucleoprotein complex composed of several viral proteins including nucleocapsid (NC). To better characterize the biochemical mechanisms of viral DNA synthesis, we overexpressed and purified recombinant HIV-1 NC and studied its effect on the activity and processivity of HIV-1 RT during polymerization of HIV-1 template sequences in vitro. The effect of NC on steady-state RT activity was dependent on the order of addition of reaction components. Addition of NC prior to formation of RT-primer.template-dNTP ternary complexes inhibited primer extension and reduced total product yields by slowing steady-state RT turnover. In contrast, addition of NC to preformed ternary complexes resulted in efficient primer extension and increased RT processivity at specific DNA template sites. NC stimulated polymerization (2-4 times) through eight of 13 sites examined in the cRRE region of HIV-1 env and increased the rate of polymerization through the D3/CTS region of HIV-1 pol 10 times. The data suggest that NC affects RT processivity by facilitating polymerization through regions of template secondary structure. Thus, NC functions as a single-strand binding (SSB)-like accessory replication factor for RT in vitro and may be part of a multicomponent retroviral replication complex.
authors.affiliation: Department of Biochemistry, University of Utah, Salt Lake City 84112, USA.
authors.forename: X
authors.initials: X
authors.lastname: Ji
authors.forename: G J
authors.initials: GJ
authors.lastname: Klarmann
authors.forename: B D
authors.initials: BD
authors.lastname: Preston
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D002213:Capsid / Q000494:pharmacology*; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D054303:HIV Reverse Transcriptase; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016133:Polymerase Chain Reaction; D012194:RNA-Directed DNA Polymerase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013698:Templates, Genetic; D014758:Viral Core Proteins / Q000494:pharmacology*
chemical_list: D017931:DNA Primers; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D014758:Viral Core Proteins; D054303:HIV Reverse Transcriptase; D012194:RNA-Directed DNA Polymerase