RESPONSES OF HELA AND CHINESE-HAMSTER OVARY P34(CDC2)/CYCLIN-B KINASE IN RELATION TO CELL-CYCLE PERTURBATIONS INDUCED BY ETOPOSIDE

  • Authors:
    • RB LOCK
    • PK KEELING
  • View Affiliations

  • Published online on: July 1, 1993     https://doi.org/10.3892/ijo.3.1.33
  • Pages: 33-42
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Abstract

The p34cdc2 kinase, which regulates the G2/M transition in eukaryotic cells, is composed of a complex between p34cdc2 and cyclin-B. The activity of this kinase, and intracellular levels of cyclin-B, achieve a maximum in the G2/M phases of both HeLa and Chinese hamster ovary (CHO) cells. The responses of p34cdc2 and cyclin-B proteins were compared between the two cell lines under conditions of G2 arrest induced by the DNA damaging agent, etoposide. p34cdc2 is a major tyrosine phosphorylated protein in the S- and G2-phases of both HeLa and CHO cells, although fundamental differences appear to exist in p34cdc2 regulation; approximately 80% of this protein is found in its hyperphosphorylated form in CHO cells compared to a maximum of 30% in HeLa cells. A brief exposure to etoposide causes both cell lines to arrest in G2, with a concomittant increase in cyclin-B levels and accumulation of hyperphosphorylated p34cdc2. Failure to activate the p34cdc2 kinase following etoposide treatment to levels comparable with synchronous G2/M-phase cells is not due to inhibition of p34cdc2/cyclin-B complex formation, but relies more on an inability to tyrosine dephosphorylate p34cdc2. Thus, regardless of apparent differences in p34cdc2/cyclin-B regulation between a human tumor and an immortalized rodent cell line, both appear to express the same G2 checkpoint for etoposide-induced DNA strand breaks, that of inhibition of p34cdc2 tyrosine dephosphorylation.

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July 1993
Volume 3 Issue 1

Print ISSN: 1019-6439
Online ISSN:1791-2423

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Spandidos Publications style
LOCK R and KEELING P: RESPONSES OF HELA AND CHINESE-HAMSTER OVARY P34(CDC2)/CYCLIN-B KINASE IN RELATION TO CELL-CYCLE PERTURBATIONS INDUCED BY ETOPOSIDE. Int J Oncol 3: 33-42, 1993.
APA
LOCK, R., & KEELING, P. (1993). RESPONSES OF HELA AND CHINESE-HAMSTER OVARY P34(CDC2)/CYCLIN-B KINASE IN RELATION TO CELL-CYCLE PERTURBATIONS INDUCED BY ETOPOSIDE. International Journal of Oncology, 3, 33-42. https://doi.org/10.3892/ijo.3.1.33
MLA
LOCK, R., KEELING, P."RESPONSES OF HELA AND CHINESE-HAMSTER OVARY P34(CDC2)/CYCLIN-B KINASE IN RELATION TO CELL-CYCLE PERTURBATIONS INDUCED BY ETOPOSIDE". International Journal of Oncology 3.1 (1993): 33-42.
Chicago
LOCK, R., KEELING, P."RESPONSES OF HELA AND CHINESE-HAMSTER OVARY P34(CDC2)/CYCLIN-B KINASE IN RELATION TO CELL-CYCLE PERTURBATIONS INDUCED BY ETOPOSIDE". International Journal of Oncology 3, no. 1 (1993): 33-42. https://doi.org/10.3892/ijo.3.1.33