Polyadenylation of c-mos mRNA as a control point in Xenopus meiotic maturation

Abstract

c-mos protein, encoded by a proto-oncogene, is essential for the meiotic maturation of frog oocytes. Polyadenylation of c-mos messenger RNA is shown here to be a pivotal regulatory step in meiotic maturation. Maturation is prevented by selective amputation of polyadenylation signals from c-mos mRNA. Injection of a prosthetic RNA, which restores c-mos polyadenylation signals by base pairing to the amputated mRNA, rescues maturation and can stimulate translation in trans. Prosthetic RNAs may provide a general strategy by which to alter patterns of mRNA expression in vivo.

Inactivation of protein kinase A is not required for c-mos translation during meiotic maturation of Xenopus oocytes

“…Polyadenylation of c-mos mRNA is known to be essential for c-mos translation and meiotic maturation in progesterone-treated oocytes (Sheets et al, 1994(Sheets et al, , 1995Gebauer et al, 1994). Thus, the above results suggested that PKA activation may have di erential e ects on polyadenylation of c-mos RNA in oocytes treated with progesterone or microinjected with recombinant c-mos.…”

“…Onset of c-mos translation has been shown to depend on increased polyadenylation of its mRNA during maturation of Xenopus oocytes (Sheets et al, 1994(Sheets et al, , 1995. Although the precise mechanism by which polyadenylation at the 3' end stimulates translation initiation at the 5' end of the message is unclear, recent studies have shown that in maturing oocytes, 3' poly(A) + addition induces 5' cap ribose methylation, and that prevention of cap ribose methylation dramatically reduces translational activation (Kuge and Richter, 1995).…”

“…However, how PKA negatively controls c-mos translation has still not been elucidated, even though control of c-mos translation in oocytes has been the subject of several recent investigations (Sheets et al, 1994(Sheets et al, , 1995Gebauer et al, 1994). The aim of the present work was to investigate the mechanism that allows PKA to suppress c-mos translation.…”

Transitioning from egg to embryo: Triggers and mechanisms of egg activation

“…Mos is a serine/threonine protein kinase that induces a cascade of serial phosphorylations that eventually end in the phosphorylation and activation of the kinase p90 RSK (Crews et al, 1992;Nebreda and Hunt, 1993;Shibuya and Ruderman, 1993). Mos is initially translated during oocyte maturation in response to progesterone (Sagata et al, 1988;Sheets et al, 1995), which is released from ovarian follicle cells upon seasonal cues (reviewed in Smith, 1989). The Mos-MAPK pathway, through p90 RSK , phosphorylates Emi2 when the levels of Emi2 accumulate during the MI/MII transition (Inoue et al, 2007;Nishiyama et al, 2007a).…”

Initiation of Xenopus Oocyte Maturation by Activation of the Mitogen-activated Protein Kinase Cascade

“…SESE-MAPKK was moderately active as compared to wild-type MAPKK. 2 To produce a more active mutant of MAPKK, a deletion (32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51) near the N-terminal was introduced into Xenopus SESE-MAPKK according to the method of Mansour et al (43) using primers (5Ј-AGCCTCGAGGTTTGTCTCGGCTGTAGGG-3Ј and 5Ј-CGTCTCGAGGCTTTTCTCACCCAGAAGC-3Ј) and was ligated at the XhoI site, yielding dSESE-MAPKK. This Xenopus dSESE-MAPKK can function as a strongly active mutant in Xenopus oocytes (this study) and in COS cells.…”