STUDIES OF MOUSE MAMMARY TUMOR VIRUS COMPOSITION AND REPLICATION (GLUCOCORTICOID, SUSPENSION, CYTOCHALASIN, COLCEMID, ACTIN).
Item
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Title
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STUDIES OF MOUSE MAMMARY TUMOR VIRUS COMPOSITION AND REPLICATION (GLUCOCORTICOID, SUSPENSION, CYTOCHALASIN, COLCEMID, ACTIN).
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Identifier
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AAI8515644
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identifier
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8515644
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Creator
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MALDARELLI, FRANK.
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Contributor
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M. J. Yagi
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Date
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1985
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Molecular
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Abstract
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Studies of mouse mammary tumor virus (MMTV) replication revealed virions purified from spent culture medium of MJY-mammary tumor cells consistently contained 7 polypeptides. Principal protein constituents were products of MMTV env gene (gp52 and gp37,7-33), and gag gene (p24, p14, p8), which were present at approximately 1850-2350 molecules each per MMTV particle. A fourth gag protein, p17, was detected, but was present in only 1079 molecules per virion. MMTV protein p44, was present in fewest numbers (350 molecules/virion), and was similar to the cytoskeletal protein actin in electrophoretic mobility and in DNase I-binding and polymerization activities. To determine whether the cytoskeleton was involved in MMTV replication, effects of microfilament-disrupting cytochalasins B and D, and of microtubule-disrupting colcemid were examined. Cytodisruptive agents altered MMTV production and polypeptide composition, but did not specifically inhibit MMTV polypeptide synthesis. Cytochalasin treatment reduced or eliminated budding MMTV particles, although levels of MMTV cell surface antigens were only slightly decreased. These data indicated proper MMTV production required an intact cytoskeleton. Exposure of mammary cells to 14(mu)M in 2-5 fold increases in synthesis of MMTV polyprotein precursors Pr76('env) and Pr76('gag), in levels of cell surface MMTV antigens, and in virion production. HC treatment also decreased env precursor Pr76('env) half-life, and altered incorporation of ('3)H-monosaccharides into precursors Pr76('env) and Pr79('env). These data suggested HC effects were not restricted to MMTV transcriptional stimulation. Prolonged HC exposure decreased MMTV production to levels obtained from untreated cells. HC-induced increases in MMTV production were obtained with increased doses of HC, or by cell passage in HC-free medium, followed by restimulation using 14 (mu)M HC. These data indicated prolonged HC exposure reversibly altered HC responsiveness. The necessity of monolayer orientation of mammary tumor cells for MMTV production was assessed by maintaining MJY-alpha cells in suspension culture. MMTV production in MJY-beta cultures was increased 10-200 fold over MJY-alpha cells. These data indicated mammary tumor cell growth and MMTV production do not require solid substratum, and that MMTV production can be stimulated by alternate growth conditions.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Biomedical Sciences
