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- Title
p42MAPK-mediated phosphorylation of xEIAP/XLX in Xenopus cytostatic factor-arrested egg extracts.
- Authors
Tsuchiya, Yuichi; Yamashita, Shigeru
- Abstract
Background: BIR family proteins are evolutionarily conserved anti-apoptotic molecules. One member of Xenopus BIR family proteins, xEIAP/XLX, is a weak apoptosis inhibitor and rapidly degraded in a cell-free apoptotic execution system derived from interphase egg extracts. However, unfertilized eggs are naturally arrested at the metaphase of meiosis II by the concerted activities of Mos-MEK-p42MAPK-p90Rsk kinase cascade (cytostatic factor pathway) and many mitotic kinases. Previous studies suggest that cytostatic factor-arrested egg extracts are more resistant to spontaneous apoptosis than interphase egg extracts in a p42MAPK-dependent manner. We tested whether xEIAP/XLX might be phosphorylated in cytostatic factor-arrested egg extracts, and also examined whether xEIAP/XLX could be functionally regulated by phosphorylation. Results: We found that p42MAPK was the major kinase phosphorylating xEIAP/XLX in cytostatic factor-arrested egg extracts, and three Ser residues (Ser 235/251/254) were identified as p42MAPK-mediated phosphorylation sites. We characterized the behaviors of various xEIAP/XLX mutants that could not be phosphorylated by p42MAPK. However, neither protein stability nor anti-apoptotic ability of xEIAP/XLX was significantly altered by the substitution of Ser with either Ala or Asp at these three sites. Conclusion: xEIAP/XLX is physiologically phosphorylated by p42MAPK in Xenopus unfertilized eggs. However, this protein may not serve as an essential mediator of p42MAPK-dependent antiapoptotic activity.
- Subjects
CELL cycle; FERTILIZATION (Biology); MEIOSIS; EGG incubation; PHOSPHORYLATION; XENOPUS; APOPTOSIS; PROTEINS
- Publication
BMC Biochemistry, 2007, Vol 8, p1
- ISSN
1471-2091
- Publication type
Article
- DOI
10.1186/1471-2091-8-5