Single cell analysis of G{sub 1} check points-the relationship between the restriction point and phosphorylation of pRb
- Department of Oncology-Pathology, Karolinska Institutet, CCK R8:04, KS 171 76 Stockholm (Sweden)
Single cell analysis allows high resolution investigation of temporal relationships between transition events in G{sub 1}. It has been suggested that phosphorylation of the retinoblastoma tumor suppressor protein (pRb) is the molecular mechanism behind passage through the restriction point (R). We performed a detailed single cell study of the temporal relationship between R and pRb phosphorylation in human fibroblasts using time lapse video-microscopy combined with immunocytochemistry. Four principally different criteria for pRb phosphorylation were used, namely (i) phosphorylation of residues Ser{sup 795} and Ser{sup 780} (ii) degree of pRb-association with the nuclear structure, a property that is closely related with pRb phosphorylation status, (iii) release of the transcription factor E2F-1 from pRb, and (iv) accumulation of cyclin E, which is dependent on phosphorylation of pRb. The analyses of individual cells revealed that passage through R preceded phosphorylation of pRb, which occurs in a gradually increasing proportion of cells in late G{sub 1}. Our data clearly suggest that pRb phosphorylation is not the molecular mechanism behind the passage through R. The restriction point and phosphorylation of pRb thus seem to represent two separate check point in G{sub 1}.
- OSTI ID:
- 20717593
- Journal Information:
- Experimental Cell Research, Vol. 305, Issue 2; Other Information: DOI: 10.1016/j.yexcr.2005.01.023; PII: S0014-4827(05)00039-X; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0014-4827
- Country of Publication:
- United States
- Language:
- English
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