| Ribonucleotide reductase--new twists in an old tale. | |
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MedLine Citation:
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PMID: 2696342 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Although they are proliferatively quiescent, the cells in the intact adult rat liver express the gene coding for the M1 subunit of ribonucleotide reductase. But since they do not need deoxyribonucleotides, they promptly inactivate the 88 to 90 kDa M1 products and degrade them into 40 kDa fragments. Partial hepatectomy signals the remaining cells to start proliferating. Two hours before the onset of DNA replication, around 16 to 18 hr after partial hepatectomy, the cells start accumulating a large pool of functional ribonucleotide reductase M2 subunits. Near the end of the G1 build-up the cells step up M1 gene expression, stop inactivating, and reduce the degradation of the M1 products. The accumulating functional 88 to 90 kDa M1 subunits, each with more than one catalytic site, couple with functional M2 subunits to produce active ribonucleotide reductase holoenzyme which accumulates in the outer nuclear membrane from which they supply deoxyribonucleotide precursors to intranuclear replication enzymes. At the end of the S phase, the cell reduces M1 gene expression and resumes degrading 88 to 90 kDa M1 subunits. At least some of the 40 kDa M1 fragments are still active and can form partially active "holoenzymes" when mixed with a standard preparation of functional M2 subunits. The M1 control mechanism appears not to operate in hepatoma cells and Ehrlich ascites tumor cells, both of which maintain a pool of undegraded 88 to 90 kDa M1 components. |
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Authors:
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J F Whitfield; M Sikorska; T Youdale; L Brewer; R Richards; P R Walker |
Publication Detail:
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Type: Journal Article; Review |
Journal Detail:
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Title: Advances in enzyme regulation Volume: 28 ISSN: 0065-2571 ISO Abbreviation: Adv. Enzyme Regul. Publication Date: 1989 |
Date Detail:
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Created Date: 1990-03-19 Completed Date: 1990-03-19 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0044263 Medline TA: Adv Enzyme Regul Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 113-23 Citation Subset: IM |
Affiliation:
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Biological Sciences Division, National Research Council of Canada, Ottawa. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Cell Line DNA Polymerase II / metabolism Liver / enzymology* Liver Regeneration Lymphoma Macromolecular Substances Mice Rats Ribonucleotide Reductases / biosynthesis, metabolism* Tumor Cells, Cultured / enzymology |
| Chemical | |
Reg. No./Substance:
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0/Macromolecular Substances; EC 1.17.4.-/Ribonucleotide Reductases; EC 2.7.7.-/DNA Polymerase II |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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