| First Author | Verlhac MH | Year | 2000 |
| Journal | EMBO J | Volume | 19 |
| Issue | 22 | Pages | 6065-74 |
| PubMed ID | 11080153 | Mgi Jnum | J:65991 |
| Mgi Id | MGI:1927701 | Doi | 10.1093/emboj/19.22.6065 |
| Citation | Verlhac MH, et al. (2000) Mos activates MAP kinase in mouse oocytes through two opposite pathways. EMBO J 19(22):6065-74 |
| abstractText | Activation of mitogen-activated protein kinase (MAPK) in maturing mouse oocytes occurs after synthesis of Mos, a MAPKKK. To investigate whether Mos acts only through MEK1, we microinjected constitutively active forms of MEK1 (MEK1S218D/S222D referred herein as MEK*) and Raf (DeltaRaf) into mouse oocytes. In mos(-/-) oocytes, which do not activate MAPK during meiosis and do not arrest in metaphase II, MEK* and DeltaRaf did not rescue MAPK activation and metaphase II arrest, whereas Mos induced a complete rescue. MEK* and DeltaRaf induced cleavage arrest of two-cell blastomeres. They induced MAPK activation when protein phosphatases were inhibited by okadaic acid, suggesting that Mos may inhibit protein phosphatases. Finally, in mos(-/-) oocytes, MEK* induced the phosphorylation of Xp42(mapk)D324N, a mutant less sensitive to dephosphorylation, showing that a MAPK phosphatase activity is present in mouse oocytes. We demonstrate that active MAPKK or MAPKKK cannot substitute for Mos to activate MAPK in mouse oocytes. We also show that a phosphatase activity inactivates MAPK, and that Mos can overcome this inhibitory activity. Thus Mos activates MAPK through two opposite pathways: activation of MEK1 and inhibition of a phosphatase. |
