Phosphorylation-related accumulation of the 125K nuclear matrix protein mitotin in human mitotic cells

N. Z. Zhelev, I. T. Todorov, R. N. Philipova, A. A. Hadjiolov*

*Corresponding author for this work

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The preparation of mammalian cells for entry into mitosis is related to a cascade of G2 phase phosphorylations of several nuclear proteins driven by mitosis-specific protein kinases. Using a monoclonal antibody we have identified previously in mammalian cells a 125K/pI 6.5 protein, associated with the nuclear matrix, and markedly increased in mitotic cells, which was named 'mitotin'. Here, we show by short-term [35S]methionine labeling of cell cycle synchronized cells that this protein is synthesized at comparable rates throughout interphase. However, upon cycloheximide block of protein synthesis mitotin labeled during S phase is rapidly degraded, while the degradation of mitotin labeled during late G2 phase is abolished, resulting in its net and marked increase. The accumulation of mitotin in premitotic and mitotic cells is related to its phosphorylation and the metabolic stability of its two phosphorylated forms. The metabolic stabilization and accumulation of a nuclear matrix protein upon phosphorylation suggests the operation of a novel mechanism among the complex events preparing the cell for mitosis.

Original languageEnglish
Pages (from-to)59-64
Number of pages6
JournalJournal of Cell Science
Volume95
Issue number1
Publication statusPublished - 1 Jan 1990
Externally publishedYes

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Nuclear Matrix-Associated Proteins
Phosphorylation
Mitosis
G2 Phase
Interphase
Cycloheximide
Nuclear Proteins
S Phase
Methionine
Protein Kinases
Cell Cycle
Proteins
Monoclonal Antibodies

Cite this

Zhelev, N. Z., Todorov, I. T., Philipova, R. N., & Hadjiolov, A. A. (1990). Phosphorylation-related accumulation of the 125K nuclear matrix protein mitotin in human mitotic cells. Journal of Cell Science, 95(1), 59-64.
Zhelev, N. Z. ; Todorov, I. T. ; Philipova, R. N. ; Hadjiolov, A. A. / Phosphorylation-related accumulation of the 125K nuclear matrix protein mitotin in human mitotic cells. In: Journal of Cell Science. 1990 ; Vol. 95, No. 1. pp. 59-64.
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Zhelev, NZ, Todorov, IT, Philipova, RN & Hadjiolov, AA 1990, 'Phosphorylation-related accumulation of the 125K nuclear matrix protein mitotin in human mitotic cells', Journal of Cell Science, vol. 95, no. 1, pp. 59-64.

Phosphorylation-related accumulation of the 125K nuclear matrix protein mitotin in human mitotic cells. / Zhelev, N. Z.; Todorov, I. T.; Philipova, R. N.; Hadjiolov, A. A.

In: Journal of Cell Science, Vol. 95, No. 1, 01.01.1990, p. 59-64.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Phosphorylation-related accumulation of the 125K nuclear matrix protein mitotin in human mitotic cells

AU - Zhelev, N. Z.

AU - Todorov, I. T.

AU - Philipova, R. N.

AU - Hadjiolov, A. A.

PY - 1990/1/1

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N2 - The preparation of mammalian cells for entry into mitosis is related to a cascade of G2 phase phosphorylations of several nuclear proteins driven by mitosis-specific protein kinases. Using a monoclonal antibody we have identified previously in mammalian cells a 125K/pI 6.5 protein, associated with the nuclear matrix, and markedly increased in mitotic cells, which was named 'mitotin'. Here, we show by short-term [35S]methionine labeling of cell cycle synchronized cells that this protein is synthesized at comparable rates throughout interphase. However, upon cycloheximide block of protein synthesis mitotin labeled during S phase is rapidly degraded, while the degradation of mitotin labeled during late G2 phase is abolished, resulting in its net and marked increase. The accumulation of mitotin in premitotic and mitotic cells is related to its phosphorylation and the metabolic stability of its two phosphorylated forms. The metabolic stabilization and accumulation of a nuclear matrix protein upon phosphorylation suggests the operation of a novel mechanism among the complex events preparing the cell for mitosis.

AB - The preparation of mammalian cells for entry into mitosis is related to a cascade of G2 phase phosphorylations of several nuclear proteins driven by mitosis-specific protein kinases. Using a monoclonal antibody we have identified previously in mammalian cells a 125K/pI 6.5 protein, associated with the nuclear matrix, and markedly increased in mitotic cells, which was named 'mitotin'. Here, we show by short-term [35S]methionine labeling of cell cycle synchronized cells that this protein is synthesized at comparable rates throughout interphase. However, upon cycloheximide block of protein synthesis mitotin labeled during S phase is rapidly degraded, while the degradation of mitotin labeled during late G2 phase is abolished, resulting in its net and marked increase. The accumulation of mitotin in premitotic and mitotic cells is related to its phosphorylation and the metabolic stability of its two phosphorylated forms. The metabolic stabilization and accumulation of a nuclear matrix protein upon phosphorylation suggests the operation of a novel mechanism among the complex events preparing the cell for mitosis.

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