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Titolo:
SITE-SPECIFIC IN-SITU AMPLIFICATION OF THE INTEGRATED POLYOMAVIRUS GENOME - A CASE FOR A CONTEXT-SPECIFIC OVER-REPLICATION MODEL OF GENE AMPLIFICATION
Autore:
SYU LJ; FLUCK MM;
Indirizzi:
MICHIGAN STATE UNIV,INTERDEPT PROGRAM CELL & MOL BIOL,DEPT MICROBIOL E LANSING MI 48824 MICHIGAN STATE UNIV,INTERDEPT PROGRAM CELL & MOL BIOL,DEPT MICROBIOL E LANSING MI 48824
Titolo Testata:
Journal of Molecular Biology
fascicolo: 1, volume: 271, anno: 1997,
pagine: 76 - 99
SICI:
0022-2836(1997)271:1<76:SIAOTI>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
VIRAL-DNA SEQUENCES; TRANSFORMED RAT-CELLS; LARGE T-ANTIGEN; VIRUS DNA; A MUTANTS; SIMIAN VIRUS-40; MOUSE CELLS; HR-T; ENHANCER; STATE;
Keywords:
POLYOMAVIRUS; INTEGRATION; LARGE T ANTIGEN; GENE AMPLIFICATION; DNA REPLICATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
57
Recensione:
Indirizzi per estratti:
Citazione:
L.J. Syu e M.M. Fluck, "SITE-SPECIFIC IN-SITU AMPLIFICATION OF THE INTEGRATED POLYOMAVIRUS GENOME - A CASE FOR A CONTEXT-SPECIFIC OVER-REPLICATION MODEL OF GENE AMPLIFICATION", Journal of Molecular Biology, 271(1), 1997, pp. 76-99

Abstract

The fate of the genome of the polyoma (Py) tumor virus following integration in the chromosomes of transformed rat FR3T3 cells was re-examined. The viral sequences were integrated at a single transformant-specific chromosomal site in each of 22 transformants tested. In situ amplification of the viral sequences was observed in 24 of 34 transformants analyzed. Large T antigen, the unique viral function involved in initiating DNA replication from the viral origin, was essential for the amplification process. There was an absolute requirement for a reiteration of viral sequences and the extent of the reiteration affected the degree of amplification The reiteration map be important for homologous recombination-mediated resolution of in situ amplified sequences. Among 11 transformants harboring a 1 to 2 kb repeat, the degree of amplification was transformant-specific and varied over a wide range. At the high end of the spectrum, the genome copy number increased 1300-foldat steady state, while at the law end, amplification was below twofold. Some aspect of the host chromatin at the site integration that affected viral gene expression, also directly or indirectly modulated the amplification. Use of high-resolution electrophoresis for the analysisof the integrated amplified sequences revealed a recurring novel pattern, consisting of a ladder with numerous bands separated by a constant distance approximately the size of the Py genome. We suggest that this pattern was generated by conversion of the amplified viral genomes to head to tail Linear arrays with cell to cell variations in the number of genome repeats at single, transformant-specific, chromosomal sites. In light of the known ''out of schedule'' firing of the Py origin,we propose an ''onion skin'' structure intermediate and present a homologous recombination model for the conversion from onion skins to linear arrays, The relevance of the in situ amplification of the Py genome to cellular gene amplification is discussed. Finally, these results clarify our understanding of the integration of the Py genome in rat cells. They suggest, that, in most cases, the multiple bands previouslydescribed in Py-transformants are likely to reflect genome amplification rather than multiple independent integration events, as assumed inthe past. This interpretation is congruent with the accepted view that the integration of the Py genome is a rare and rate-limiting event in transformation. (C) 1997 Academic Press Limited.

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Documento generato il 04/12/20 alle ore 01:29:31