title: Repression of the Chromatin-Tethering Domain of Murine Leukemia Virus p12.
abstract: Murine leukemia virus (MLV) p12, encoded within Gag, binds the viral preintegration complex (PIC) to the mitotic chromatin. This acts to anchor the viral PIC in the nucleus as the nuclear envelope re-forms postmitosis. Mutations within the p12 C terminus (p12 PM13 to PM15) block early stages in viral replication. Within the p12 PM13 region (p1260PSPMA65), our studies indicated that chromatin tethering was not detected when the wild-type (WT) p12 protein (M63) was expressed as a green fluorescent protein (GFP) fusion; however, constructs bearing p12-I63 were tethered. N-terminal truncations of the activated p12-I63-GFP indicated that tethering increased further upon deletion of p1225DLLTEDPPPY34, which includes the late domain required for viral assembly. The p12 PM15 sequence (p1270RREPP74) is critical for wild-type viral viability; however, virions bearing the PM15 mutation (p1270AAAAA74) with a second M63I mutant were viable, with a titer 18-fold lower than that of the WT. The p12 M63I mutation amplified chromatin tethering and compensated for the loss of chromatin binding of p12 PM15. Rescue of the p12-M63-PM15 nonviable mutant with prototype foamy virus (PFV) and Kaposi's sarcoma herpesvirus (KSHV) tethering sequences confirmed the function of p1270-74in chromatin binding. Minimally, full-strength tethering was seen with only p1261SPIASRLRGRR71fused to GFP. These results indicate that the p12 C terminus alone is sufficient for chromatin binding and that the presence of the p1225DLLTEDPPPY34motif in the N terminus suppresses the ability to tether.
  
  
  OBJECTIVE
  This study defines a regulatory mechanism controlling the differential roles of the MLV p12 protein in early and late replication. During viral assembly and egress, the late domain within the p12 N terminus functions to bind host vesicle release factors. During viral entry, the C terminus of p12 is required for tethering to host mitotic chromosomes. Our studies indicate that the p12 domain including the PPPY late sequence temporally represses the p12 chromatin tethering motif. Maximal p12 tethering was identified with only an 11-amino-acid minimal chromatin tethering motif encoded at p1261-71Within this region, the p12-M63I substitution switches p12 into a tethering-competent state, partially rescuing the p12-PM15 tethering mutant. A model for how this conformational change regulates early versus late functions is presented.
authors.affiliation: Rutgers-Robert Wood Johnson Medical School, Department of Pharmacology, Piscataway, New Jersey, USA.
authors.forename: Jonathon D
authors.identifier: http://orcid.org/0000-0001-8669-2754
authors.initials: JD
authors.lastname: Brzezinski
authors.affiliation: The School of Arts and Sciences, Rutgers University, New Brunswick, New Jersey, USA.
authors.forename: Apexa
authors.identifier: http://orcid.org/0000-0001-8343-598X
authors.initials: A
authors.lastname: Modi
authors.affiliation: The School of Arts and Sciences, Rutgers University, New Brunswick, New Jersey, USA.
authors.forename: Mengdan
authors.identifier: http://orcid.org/0000-0003-2057-723X
authors.initials: M
authors.lastname: Liu
authors.affiliation: Rutgers-Robert Wood Johnson Medical School, Department of Pharmacology, Piscataway, New Jersey, USA roth@rwjms.rutgers.edu.
authors.forename: Monica J
authors.identifier: http://orcid.org/0000-0002-2219-0402
authors.initials: MJ
authors.lastname: Roth
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism* / Q000821:virology; D005786:Gene Expression Regulation; D015683:Gene Products, gag / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D057809:HEK293 Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D051379:Mice; D008938:Mitosis; D008979:Moloney murine leukemia virus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D009154:Mutation; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014771:Virion / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D019065:Virus Assembly; D014779:Virus Replication
chemical_list: D002843:Chromatin; C468293:Gag protein p12, moloney murine leukemia virus; D015683:Gene Products, gag; D011993:Recombinant Fusion Proteins