title: The TY3 Gag3 spacer controls intracellular condensation and uncoating.
abstract: Cells expressing the yeast retrotransposon Ty3 form concentrated foci of Ty3 proteins and RNA within which virus-like particle (VLP) assembly occurs. Gag3, the major structural protein of the Ty3 retrotransposon, is composed of capsid (CA), spacer (SP), and nucleocapsid (NC) domains analogous to retroviral domains. Unlike the known SP domains of retroviruses, Ty3 SP is highly acidic. The current studies investigated the role of this domain. Although deletion of Ty3 SP dramatically reduced retrotransposition, significant Gag3 processing and cDNA synthesis occurred. Mutations that interfered with cleavage at the SP-NC junction disrupted CA-SP processing, cDNA synthesis, and electron-dense core formation. Mutations that interfered with cleavage of CA-SP allowed cleavage of the SP-NC junction, production of electron-dense cores, and cDNA synthesis but blocked retrotransposition. A mutant in which acidic residues of SP were replaced with alanine failed to form both Gag3 foci and VLPs. We propose a speculative "spring" model for Gag3 during assembly. In the first phase during concentration of Gag3 into foci, intramolecular interactions between negatively charged SP and positively charged NC domains of Gag3 limit multimerization. In the second phase, the NC domain binds RNA, and the bound form is stabilized by intermolecular interactions with the SP domain. These interactions promote CA domain multimerization. In the third phase, a negatively charged SP domain destabilizes the remaining CA-SP shell for cDNA release.
authors.affiliation: Department of Biological Chemistry, University of California, Irvine, Irvine CA 92697, USA.
authors.forename: Kristina
authors.initials: K
authors.lastname: Clemens
authors.forename: Liza
authors.initials: L
authors.lastname: Larsen
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Yurii
authors.initials: Y
authors.lastname: Kuznetsov
authors.forename: Virginia
authors.initials: V
authors.lastname: Bilanchone
authors.forename: Arlo
authors.initials: A
authors.lastname: Randall
authors.forename: Adam
authors.initials: A
authors.lastname: Harned
authors.forename: Rhonda
authors.initials: R
authors.lastname: Dasilva
authors.forename: Kunio
authors.initials: K
authors.lastname: Nagashima
authors.forename: Alexander
authors.initials: A
authors.lastname: McPherson
authors.forename: Pierre
authors.initials: P
authors.lastname: Baldi
authors.forename: Suzanne
authors.initials: S
authors.lastname: Sandmeyer
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D018076:DNA, Complementary / Q000378:metabolism; D004271:DNA, Fungal / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D012331:RNA, Fungal / Q000378:metabolism*; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism*; D018626:Retroelements / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018076:DNA, Complementary; D004271:DNA, Fungal; C429283:MDV1 protein, S cerevisiae; D012331:RNA, Fungal; D018626:Retroelements; D029701:Saccharomyces cerevisiae Proteins; D012194:RNA-Directed DNA Polymerase; C496084:reverse transcriptase Ty3, S cerevisiae