Either cyclin B1 or B2 is necessary and sufficient for inducing germinal vesicle breakdown during frog (Rana japonica) oocyte maturation

Abstract

Oocyte maturation is finally triggered by the maturation‐promoting factor (MPF), which consists of Cdc2 and cyclin B. We have cloned cDNAs encoding frog (Rana japonica) cyclins B1 and B2 and produced antibodies against their products. Using the antibodies, we investigated changes in protein states and levels of Cdc2 and cyclins B1 and B2 during oocyte maturation. In immature oocytes, all Cdc2 was a monomeric unphosphorylated inactive 35 kDa form and neither cyclin B1 nor cyclin B2 was present. Mature oocytes contained the MPF complex consisting of an active 34 kDa Cdc2 phosphorylated on threonine161 and a 49 kDa cyclin B1 or a 51 kDa cyclin B2. After progesterone stimulation, both cyclins B1 and B2 were synthesized from their stored mRNAs and bound to the preexisting 35 kDa Cdc2. The binding of Cdc2 with cyclin B and its activation probably through the phosphorylation on threonine161 occurred at almost the same time, in accordance with an electrophoretic mobility shift of Cdc2 from 35 to 34 kDa. Microinjection into immature oocytes of cyclin B1 or B2 mRNA alone, or a mixture of them, induced germinal vesicle breakdown (GVBD) with similar dose‐dependence. When the translation of endogenous mRNAs of both cyclins B1 and B2 was inhibited with antisense RNAs, progesterone failed to induce GVBD in the oocytes, but the inhibition of only one of the two was unable to inhibit the progesterone‐induced GVBD. These results indicate that either cyclin B1 or B2 is necessary and sufficient for inducing GVBD during Rana oocyte maturation. Mol. Reprod. Dev. 50:499–509, 1998. © 1998 Wiley‐Liss, Inc.

Biochemical Identification of Xenopus Pumilio as a Sequence-specific Cyclin B1 mRNA-binding Protein That Physically Interacts with a Nanos Homolog, Xcat-2, and a Cytoplasmic Polyadenylation Element-binding Protein

“…NRE-like motifs are found in the 3Ј-UTR of cyclin B1 mRNA in fish and amphibians, including goldfish (41), medaka (42), zebrafish, 2 Xenopus (43), and Rana (44). It is therefore expected that a homolog of Pumilio or its related protein(s) binds directly to cyclin B1 mRNA to control its translation.…”

Possible Involvement of Phosphatidylinositol 3-Kinase, but Not Protein Kinase B or Glycogen Synthase Kinase 3β, in Progesterone-Induced Oocyte Maturation in the Japanese Brown Frog, Rana japonica

“…Then CAK phosphorylates Cyclin B-bound Cdc2 on T161. Neither T14/Y15 phosphorylation nor its dephosphorylation is involved in MPF activation in Rana (Ihara et al, 1998). Other amphibians except Xenopus probably utilize similar mechanisms (Tanaka and Yamashita, 1995;Sakamoto et al, 1998).…”

“…Immature oocytes were isolated with collagenase as described previously (Ihara et al, 1998). All of the experiments were carried out at room temperature unless otherwise noted.…”

Cdc2-Cyclin B–Induced G2 to M Transition in Perch Oocyte Is Dependent on Cdc251

“…This is a complex of two proteins, a regulatory component called cyclin B and the catalytic component protein kinase known as cyclin-dependent kinase, Cdc2 [12][13][14][15]. Several investigators attempted to explain molecular mechanisms of MPF formation and activation during oocyte maturation in different species [16][17][18][19][20][21] and found that despite the common molecular structure of MPF in eukaryotes, mechanisms involved in active MPF formation differ [22][23][24][25][26][27].…”