title: Human immunodeficiency virus type 1 Vpr induces G2 checkpoint activation by interacting with the splicing factor SAP145.
abstract: Vpr, the viral protein R of human immunodeficiency virus type 1, induces G(2) cell cycle arrest and apoptosis in mammalian cells via ATR (for "ataxia-telangiectasia-mediated and Rad3-related") checkpoint activation. The expression of Vpr induces the formation of the gamma-histone 2A variant X (H2AX) and breast cancer susceptibility protein 1 (BRCA1) nuclear foci, and a C-terminal domain is required for Vpr-induced ATR activation and its nuclear localization. However, the cellular target of Vpr, as well as the mechanism of G(2) checkpoint activation, was unknown. Here we report that Vpr induces checkpoint activation and G(2) arrest by binding to the CUS1 domain of SAP145 and interfering with the functions of the SAP145 and SAP49 proteins, two subunits of the multimeric splicing factor 3b (SF3b). Vpr interacts with and colocalizes with SAP145 through its C-terminal domain in a speckled distribution. The depletion of either SAP145 or SAP49 leads to checkpoint-mediated G(2) cell cycle arrest through the induction of nuclear foci containing gamma-H2AX and BRCA1. In addition, the expression of Vpr excludes SAP49 from the nuclear speckles and inhibits the formation of the SAP145-SAP49 complex. To conclude, these results point out the unexpected roles of the SAP145-SAP49 splicing factors in cell cycle progression and suggest that cellular expression of Vpr induces checkpoint activation and G(2) arrest by interfering with the function of SAP145-SAP49 complex in host cells.
authors.affiliation: Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA. terad002@umn.edu
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Terada
authors.forename: Yuko
authors.initials: Y
authors.lastname: Yasuda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D016195:G2 Phase / Q000502:physiology*; D016336:Gene Products, vpr / Q000235:genetics / Q000378:metabolism*; D018816:Genes, cdc; D015497:HIV-1 / Q000378:metabolism*; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing; D000072260:RNA Splicing Factors; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D020798:Two-Hybrid System Techniques; D054325:vpr Gene Products, Human Immunodeficiency Virus
chemical_list: D019313:BRCA1 Protein; D016336:Gene Products, vpr; C468783:H2AX protein, human; D006657:Histones; D010750:Phosphoproteins; D021122:Protein Subunits; D000072260:RNA Splicing Factors; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D017413:Ribonucleoprotein, U2 Small Nuclear; C486348:SF3B2 protein, human; C486347:SF3B4 protein, human; D054325:vpr Gene Products, Human Immunodeficiency Virus