title: Nucleolar localization of mouse mammary tumor virus proteins in T-cell lymphomas.
abstract: To characterize novel proteins expressed in lymphoma cells, monoclonal antibodies (MAbs) were raised against variant S49 mouse lymphoma cells. Immunoperoxidase analysis with a specific MAb, named M-66, revealed nuclear localization with prominent staining in the nucleoli of both tumorigenic (T-63) cells and nontumorigenic, immunogenic (T-25-Adh) cells. Weak signals were also observed in the cytoplasm and plasma membrane of both cells. Western blot analysis with M-66 antibody revealed a 14-kDa protein in nuclear extracts of both T-25-Adh and T-63 cells. An additional nuclear 21-kDa protein was evident only in T-63 cells. M-66 identified several clones from a T-25-Adh cDNA expression library. These clones demonstrated extensive homology (approximately 95% identity throughout their length) to the mouse mammary tumor virus (MMTV) env and LTR regions. Extensive amino acid sequence homology (approximately 90% identity) between the clones and the env protein was observed. M-66 identified the 14-kDa protein in another MMTV bearing T-cell lymphoma, EL-4. Immunoperoxidase analysis of EL-4 cells with M-66 also revealed prominent nucleolar staining. MMTV-negative cells and MMTV-positive cells of nonlymphocytic origin were devoid of both 14- and 21-kDa proteins. Moreover, an anti-MMTV gp52 (env) antibody precipitated the 21-kDa protein in T-63 cells. We thus suggest that MMTV bearing T-cell lymphomas express nucleolar proteins translated from the env region of MMTV.
authors.affiliation: Department of Cell and Animal Biology, Hebrew University of Jerusalem, Israel.
authors.forename: H
authors.initials: H
authors.lastname: Hoch-Marchaim
authors.forename: T
authors.initials: T
authors.lastname: Hasson
authors.forename: E
authors.initials: E
authors.lastname: Rorman
authors.forename: S
authors.initials: S
authors.lastname: Cohen
authors.forename: J
authors.initials: J
authors.lastname: Hochman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D000957:Antigens, Viral, Tumor / Q000378:metabolism*; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002466:Cell Nucleolus / Q000378:metabolism* / Q000821:virology; D003593:Cytoplasm / Q000378:metabolism; D004273:DNA, Neoplasm / Q000032:analysis; D015723:Gene Library; D007124:Immunoenzyme Techniques; D016399:Lymphoma, T-Cell / Q000378:metabolism* / Q000648:ultrastructure / Q000821:virology*; D008324:Mammary Tumor Virus, Mouse / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D000957:Antigens, Viral, Tumor; D004273:DNA, Neoplasm; D009687:Nuclear Proteins; D014759:Viral Envelope Proteins