Distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation.

Phosphorylation of the retinoblastoma protein (pRB) is assumed to regulate its growth-controlling function. Moreover, hypophosphorylated and hyperphosphorylated forms of pRB can be distinguished by virtue of the distinct affinities with which they bind to the cell nucleus. This property allows the i...

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Main Authors: Mittnacht, S, Lees, J A, Desai, D, Harlow, E, Morgan, D O, Weinberg, R A
Formato: Artigo
Idioma:en
Publicado em: 1994
Assuntos:
Research Article
Acesso em linha:https://ncbi.nlm.nih.gov/pmc/articles/PMC394785/
https://ncbi.nlm.nih.gov/pubmed/8306955
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spelling pubmed-3947852005-04-27 Distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation. Mittnacht, S Lees, J A Desai, D Harlow, E Morgan, D O Weinberg, R A EMBO J Research Article Phosphorylation of the retinoblastoma protein (pRB) is assumed to regulate its growth-controlling function. Moreover, hypophosphorylated and hyperphosphorylated forms of pRB can be distinguished by virtue of the distinct affinities with which they bind to the cell nucleus. This property allows the identification of individual cell nuclei that contain pRB in one or the other form. We show here that after cells emerge from a quiescent (G0) state, conversion of their complement of pRB into a hyperphosphorylated form occurs in late G1, preceding entry into S phase by several hours. Thus, contrary to earlier reports, pRB phosphorylation is not co-ordinated with the G1-S transition and may not directly regulate it. A distinct set of phosphopeptides is found exclusively in those forms of pRB that show the loose nuclear association characteristic of the hyperphosphorylated form of pRB. Another set of phosphopeptides is found with both hypophosphorylated and hyperphosphorylated forms. This suggests the existence of distinct patterns of phosphorylation that are associated with different subsets of pRB molecules. We conclude that substantial phosphorylation of pRB exists in G1 even prior to the hyperphosphorylation point. Cyclin-dependent kinases can cause a liberation of pRB from cell nuclei in vitro. Phosphorylation by members of this kinase family is therefore likely to be directly involved in the change in nuclear affinity in vivo and the associated changes in pRB functioning. 1994-01-01 /pmc/articles/PMC394785/ /pubmed/8306955 Text en
institution US National Library of Medicine
collection PubMed Central
language en
format Article
topic Research Article
spellingShingle Research Article
Mittnacht, S
Lees, J A
Desai, D
Harlow, E
Morgan, D O
Weinberg, R A
Distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation.
description Phosphorylation of the retinoblastoma protein (pRB) is assumed to regulate its growth-controlling function. Moreover, hypophosphorylated and hyperphosphorylated forms of pRB can be distinguished by virtue of the distinct affinities with which they bind to the cell nucleus. This property allows the identification of individual cell nuclei that contain pRB in one or the other form. We show here that after cells emerge from a quiescent (G0) state, conversion of their complement of pRB into a hyperphosphorylated form occurs in late G1, preceding entry into S phase by several hours. Thus, contrary to earlier reports, pRB phosphorylation is not co-ordinated with the G1-S transition and may not directly regulate it. A distinct set of phosphopeptides is found exclusively in those forms of pRB that show the loose nuclear association characteristic of the hyperphosphorylated form of pRB. Another set of phosphopeptides is found with both hypophosphorylated and hyperphosphorylated forms. This suggests the existence of distinct patterns of phosphorylation that are associated with different subsets of pRB molecules. We conclude that substantial phosphorylation of pRB exists in G1 even prior to the hyperphosphorylation point. Cyclin-dependent kinases can cause a liberation of pRB from cell nuclei in vitro. Phosphorylation by members of this kinase family is therefore likely to be directly involved in the change in nuclear affinity in vivo and the associated changes in pRB functioning.
author Mittnacht, S
Lees, J A
Desai, D
Harlow, E
Morgan, D O
Weinberg, R A
author_facet Mittnacht, S
Lees, J A
Desai, D
Harlow, E
Morgan, D O
Weinberg, R A
author_sort Mittnacht, S
title Distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation.
title_short Distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation.
title_full Distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation.
title_fullStr Distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation.
title_full_unstemmed Distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation.
title_sort distinct sub-populations of the retinoblastoma protein show a distinct pattern of phosphorylation.
publishDate 1994
url https://ncbi.nlm.nih.gov/pmc/articles/PMC394785/
https://ncbi.nlm.nih.gov/pubmed/8306955
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