title: Minichromosome maintenance 2 bound with retroviral Gp70 is localized to cytoplasm and enhances DNA-damage-induced apoptosis.
abstract: The interaction of viral proteins with host-cellular proteins elicits the activation of cellular signal transduction pathways and possibly leads to viral pathogenesis as well as cellular biological events. Apoptotic signals induced by DNA-damage are remarkably up-regulated by Friend leukemia virus (FLV) exclusively in C3H hosts; however, the mechanisms underlying the apoptosis enhancement and host-specificity are unknown. Here, we show that C3H mouse-derived hematopoietic cells originally express higher levels of the minichromosome maintenance (MCM) 2 protein than BALB/c- or C57BL/6-deriverd cells, and undergo more frequent apoptosis following doxorubicin-induced DNA-damage in the presence of the FLV envelope protein gp70. Dual transfection with gp70/Mcm2 reproduced doxorubicin-induced apoptosis even in BALB/c-derived 3T3 cells. Immunoprecipitation assays using various deletion mutants of MCM2 revealed that gp70 bound to the nuclear localization signal (NLS) 1 (amino acids 18-24) of MCM2, interfered with the function of NLS2 (amino acids 132-152), and suppressed the normal nuclear-import of MCM2. Cytoplasmic MCM2 reduced the activity of protein phosphatase 2A (PP2A) leading to the subsequent hyperphosphorylation of DNA-dependent protein kinase (DNA-PK). Phosphorylated DNA-PK exhibited elevated kinase activity to phosphorylate P53, thereby up-regulating p53-dependent apoptosis. An apoptosis-enhancing domain was identified in the C-terminal portion (amino acids 703-904) of MCM2. Furthermore, simultaneous treatment with FLV and doxorubicin extended the survival of SCID mice bearing 8047 leukemia cells expressing high levels of MCM2. Thus, depending on its subcellular localization, MCM2 plays different roles. It participates in DNA replication in the nucleus as shown previously, and enhances apoptosis in the cytoplasm.
authors: Department of Comprehensive Pathology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors: Shinya
authors: S
authors: Abe
authors: Morito
authors: M
authors: Kurata
authors: Shiho
authors: S
authors: Suzuki
authors: Kouhei
authors: K
authors: Yamamoto
authors: Ken-ichi
authors: K
authors: Aisaki
authors: Jun
authors: J
authors: Kanno
authors: Masanobu
authors: M
authors: Kitagawa
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism*; D004249:DNA Damage / Q000235:genetics; D051747:DNA-Activated Protein Kinase / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D005622:Friend murine leukemia virus / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D064111:Minichromosome Maintenance Complex Component 2; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012192:Retroviridae Infections / Q000235:genetics / Q000473:pathology / Q000821:virology; D014162:Transfection; D014759:Viral Envelope Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; C576318:Mcm2 protein, mouse; D050505:Mutant Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014759:Viral Envelope Proteins; D004317:Doxorubicin; D051747:DNA-Activated Protein Kinase; D054648:Protein Phosphatase 2; D064111:Minichromosome Maintenance Complex Component 2