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

Abstract

The G2 to M phase transition in perch oocytes is regulated by maturation promoting factor (MPF), a complex of Cdc2 and cyclin B. In Anabas testudineus, a fresh water perch, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one, the maturation inducing hormone (MIH), induced complete germinal vesicle breakdown (GVBD) of oocytes at 21 h. An unusual cyclin, p30 cyclin B, has been identified in oocyte extract using both monoclonal and polyclonal antibodies. Surprisingly, Cdc2 could not be identified, although a Northern blot with Cdc2 cDNA demonstrated expression of the gene. Purification of MPF through an immunoaffinity column followed by SDS-PAGE showed three proteins, Cdc2, cyclin B, and a 20 kDa fragment, indicating earlier failure in immunodetection may be due to the interference by this fragment. In uninduced oocytes, p30 cyclin B was present, and its expression was increased by MIH. MIH increased p30 cyclin B accumulation at 3 h, a high level which was maintained between 9 and 21 h, but an effective increase in GVBD and H1 kinase activation could only be observed between 15 and 21 h. This delay in active MPF formation was found to be related to the activation of Cdc25, phosphorylation of which was detected at 12 h, and a substantial increase occurred during 15-18 h. Sodium orthovanadate, a tyrosine phosphatase inhibitor, inhibited H1 kinase activity and GVBD, suggesting the requirement of Cdc25 activity in MPF activation. Our results show occurrence of pre-MPF in uninduced oocytes and its conversion to active MPF requires dephosphorylation by Cdc25, the existence of which has not yet been shown in fish.

Ochratoxin A induces DNA damage and G2 phase arrest in human esophageal epithelium Het-1A cells <i>in vitro </i>

“…The transition of cells from G2 into mitosis is dependent upon the completion of several events that culminate in the activation of the cyclin B1/Cdc2-kinase protein complex (Gautier et al, 1990;Basu et al, 2004). Several lines reports showed that G2 or G2/M arrest could be induced by down-regulation of Cdc2 in different kinds of cells (Hostein et al, 2001;Kim et al, 1999).…”

Activation of both Mos and Cdc25 is required for G2‐M transition in perch oocyte

“…Prior to our demonstration about the presence of Cdc25 in Anabas oocyte (Basu et al, 2004), it had not been reported in other fish species. Perch cdc25 is encoded by a 3,104 bp nucleotide sequence.…”

“…Studies have demonstrated that although MPF has a common molecular structure throughout the animal kingdom, the regulation of its function ß 2008 WILEY-LISS, INC. varies among different species (Ihara et al, 1998;Ferby et al, 1999;Katsu et al, 1999;Kishimoto 1999;McGowan 2003;Ye et al, 2003). We have shown earlier that in Anabas testudineus, the mechanism of oocyte maturation has some resemblances to the Xenopus model and does not conform to the fish model (Basu et al, 2004). Progesterone induces activation of two parallel signaling pathways in Xenopus that converge on the activation of cyclin B/Cdk1 (Stanford et al, 2003).…”

“…One pathway inhibits an inhibitor of Cdk1 (Wee1/ Myt1 kinase) and the other activates an activator of Cdk1 (Cdc25 phosphatase). We have earlier reported that MPF activity in Anabas is characterized by the presence of inactive pre-MPF and is related to the activation of Cdc25, a dual specificity phosphatase that converts the inactive pre-MPF to active MPF (Basu et al, 2004). Here lies an important question, whether both pathways, that is, inactivation of Myt1 and activation of Cdc25 are obligatory or if the operation of either one would rescue the oocyte to ensure G2-M transition.…”

Multiple pathways were involved in tubeimoside-1-induced cytotoxicity of HeLa cells

“…Obviously, the effects of TBMS1-mediated G2/M arrest were positively correlated with the TBMS1-stimulated cancer cell apoptosis. Cdc2, also known as Cdk1, forms a heterodimeric complex with Cyclin B1 in nucleus to drive the cell from G2 to M phase [33,34]. TBMS1 decreased Cdc2 and Cyclin B1 protein levels, with a concomitant decrease in Cdc2 kinase activity in HeLa cells (Fig.…”