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Initiation of DNA synthesis in the prematurely condensed chromosomes of G1 cells.
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MedLine Citation:
PMID:  7419597     Owner:  NLM     Status:  MEDLINE    
The objective of this study was to investigate whether G1 cells could enter S phase after premature chromosome condensation resulting from fusion with mitotic cells. HeLa cell synchronized in early G1, mid-G1, late G1, and G2 and human diploid fibroblasts synchronized in G0 and G1 phases were separately fused by use of UV-inactivated Sendai virus with mitotic HeLa cells. After cell fusion and premature chromosome condensation, the fused cells were incubated in culture medium containing Colcemid (0.05 micrograms/ml) and [3H]thymidine ([3H]ThdR) (0.5 microCi/ml; sp act, 6.7 Ci/mM). At 0, 2, 4, and 6 h after fusion, cell samples were taken to determine the initation of DNA synthesis in the prematurely condensed chromosomes (PCC) on the basis of their morphology and labeling index. The results of this study indicate that PCC from G0, G1, and G2 cells reach the maximum degree of compaction or condensation at 2 h after PCC induction. In addition, the G1-PCC from normal and transformed cells initiated DNA synthesis, as indicated by their "pulverized" appearance and incorporation of [3H]ThdR. Further, the initiation of DNA synthesis in G1-PCC occurred significantly earlier than in the mononucleate G1 cells. Neither pulverization nor incorporation of label was observed in the PCC of G0 and G2 cells. These findings suggest that chromosome decondensation, although not controlling the timing of a cell's entry into S phase, is an important step for the initiation of DNA synthesis. These data also suggest that the entry of a S phase may be regulated by cell cycle phase-specific changes in the permeability of the nuclear envelope to the inducers of DNA synthesis present in the cytoplasm.
S K Hanks; P N Rao
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of cell biology     Volume:  87     ISSN:  0021-9525     ISO Abbreviation:  J. Cell Biol.     Publication Date:  1980 Oct 
Date Detail:
Created Date:  1980-12-18     Completed Date:  1980-12-18     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0375356     Medline TA:  J Cell Biol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  285-91     Citation Subset:  IM    
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MeSH Terms
Cell Cycle*
Cell Fusion
Cell Line
Chromosomes / physiology*,  ultrastructure
DNA Replication*
Nuclear Envelope / metabolism
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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Journal Information
Journal ID (nlm-ta): J Cell Biol
ISSN: 0021-9525
ISSN: 1540-8140
Publisher: The Rockefeller University Press
Article Information
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Print publication date: Day: 1 Month: 10 Year: 1980
Volume: 87 Issue: 1
First Page: 285 Last Page: 291
ID: 2110714
Publisher Id: 81026443
PubMed Id: 7419597

Initiation of DNA synthesis in the prematurely condensed chromosomes of G1 cells

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