Involvement of Chk1 kinase in prophase I arrest of Xenopus oocytes

Nobushige Nakajo, Tomoya Oe, Katsuhiro Uto, Noriyuki Sagata

Research output: Contribution to journalArticle

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Abstract

Chk1 kinase, a DNA damage/replication G2 checkpoint kinase, has recently been shown to phosphorylate and inhibit Cdc25C, a Cdc2 Tyr-15 phosphatase, thereby directly linking the G2 checkpoint to negative regulation of Cdc2. Immature Xenopus oocytes are arrested naturally at the first meiotic prophase (prophase I) or the late G2 phase, with sustained Cdc2 Tyr-15 phosphorylation. Here we have cloned a Xenopus homolog of Chk1, determined its developmental expression, and examined its possible role in prophase I arrest of oocytes. Xenopus Chk1 protein is expressed at approximately constant levels throughout oocyte maturation and early embryogenesis. Overexpression of wild-type Chk1 in oocytes prevents the release from prophase I arrest by progesterone. Conversely, specific inhibition of endogenous Chk1 either by overexpression of a dominant-negative Chk1 mutant or by injection of a neutralizing anti-Chk1 antibody facilitates prophase I release by progesterone. Moreover, when ectopically expressed in oocytes, a Chk1-nonphosphorylatable Cdc25C mutant alone can induce prophase I release much more efficiently than wild-type Cdc25C; if endogenous Chk1 function is inhibited, however, even wild-type Cdc25C can induce the release very efficiently. These results suggest strongly that Chk1 is involved in physiological prophase I arrest of Xenopus oocytes via the direct phosphorylation and inhibition of Cdc25C. We discuss the possibility that Chk1 might function either as a G2 checkpoint kinase or as an ordinary cell cycle regulator in prophase-I-arrested oocytes.

Original languageEnglish
Pages (from-to)432-444
Number of pages13
JournalDevelopmental Biology
Volume207
Issue number2
DOIs
Publication statusPublished - Mar 15 1999

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Meiotic Prophase I
Xenopus
Oocytes
Progesterone
Phosphotransferases
Xenopus Proteins
Phosphorylation
Prophase
G2 Phase
Checkpoint Kinase 1
Neutralizing Antibodies
DNA Replication
Phosphoric Monoester Hydrolases
DNA Damage
Embryonic Development
Anti-Idiotypic Antibodies
Cell Cycle
Injections

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

Cite this

Involvement of Chk1 kinase in prophase I arrest of Xenopus oocytes. / Nakajo, Nobushige; Oe, Tomoya; Uto, Katsuhiro; Sagata, Noriyuki.

In: Developmental Biology, Vol. 207, No. 2, 15.03.1999, p. 432-444.

Research output: Contribution to journalArticle

Nakajo, Nobushige ; Oe, Tomoya ; Uto, Katsuhiro ; Sagata, Noriyuki. / Involvement of Chk1 kinase in prophase I arrest of Xenopus oocytes. In: Developmental Biology. 1999 ; Vol. 207, No. 2. pp. 432-444.
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