title: C-terminal domain modulates the nucleic acid chaperone activity of human T-cell leukemia virus type 1 nucleocapsid protein via an electrostatic mechanism.
abstract: Retroviral nucleocapsid (NC) proteins are molecular chaperones that facilitate nucleic acid (NA) remodeling events critical in viral replication processes such as reverse transcription. Surprisingly, the NC protein from human T-cell leukemia virus type 1 (HTLV-1) is an extremely poor NA chaperone. Using bulk and single molecule methods, we find that removal of the anionic C-terminal domain (CTD) of HTLV-1 NC results in a protein with chaperone properties comparable with that of other retroviral NCs. Increasing the ionic strength of the solution also improves the chaperone activity of full-length HTLV-1 NC. To determine how the CTD negatively modulates the chaperone activity of HTLV-1 NC, we quantified the thermodynamics and kinetics of wild-type and mutant HTLV-1 NC/NA interactions. The wild-type protein exhibits very slow dissociation kinetics, and removal of the CTD or mutations that eliminate acidic residues dramatically increase the protein/DNA interaction kinetics. Taken together, these results suggest that the anionic CTD interacts with the cationic N-terminal domain intramolecularly when HTLV-1 NC is not bound to nucleic acids, and similar interactions occur between neighboring molecules when NC is NA-bound. The intramolecular N-terminal domain-CTD attraction slows down the association of the HTLV-1 NC with NA, whereas the intermolecular interaction leads to multimerization of HTLV-1 NC on the NA. The latter inhibits both NA/NC aggregation and rapid protein dissociation from single-stranded DNA. These features make HTLV-1 NC a poor NA chaperone, despite its robust duplex destabilizing capability.
authors.affiliation: Department of Chemistry and Biochemistry, Center for Retrovirus Research, Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Dominic F
authors.initials: DF
authors.lastname: Qualley
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Stewart-Maynard
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.forename: Mithun
authors.initials: M
authors.lastname: Mitra
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gorelick
authors.forename: Ioulia
authors.initials: I
authors.lastname: Rouzina
authors.forename: Mark C
authors.initials: MC
authors.lastname: Williams
authors.forename: Karin
authors.initials: K
authors.lastname: Musier-Forsyth
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D015368:Human T-lymphotropic virus 1 / Q000737:chemistry*; D007700:Kinetics; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation / Q000187:drug effects; D009691:Nucleic Acid Denaturation / Q000187:drug effects; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry; D009696:Nucleic Acids / Q000378:metabolism*; D019590:Nucleocapsid Proteins / Q000737:chemistry; D009994:Osmolar Concentration; D017434:Protein Structure, Tertiary; D012367:RNA, Viral / Q000737:chemistry; D012965:Sodium Chloride / Q000494:pharmacology; D012996:Solutions; D055672:Static Electricity; D016335:Zinc Fingers
chemical_list: D004279:DNA, Viral; D018832:Molecular Chaperones; D050505:Mutant Proteins; D009692:Nucleic Acid Heteroduplexes; D009696:Nucleic Acids; D019590:Nucleocapsid Proteins; D012367:RNA, Viral; D012996:Solutions; D012965:Sodium Chloride