NCBI Summary:
This gene, which has a previous symbol of UNG2, was erroneously identified as a uracil DNA glycosylase in PubMed ID: 2001396. A later publication, PubMed ID: 8419333, identified this gene's product as a cyclin protein family member. The UNG2 term is also used as a specific protein isoform name for the UNG gene (GeneID 7374), so confusion exists in the scientific literature and in some databases for these two genes.[provided by RefSeq, Nov 2010]
General function
Enzyme
Comment
Cellular localization
Cytoplasmic
Comment
Ovarian function
Oocyte maturation
Comment
Cyclin O Regulates Germinal Vesicle Breakdown in Mouse Oocytes. Ma JY et al. It is well accepted that oocyte meiotic resumption is mainly regulated by the maturation promoting factor (MPF) which is composed of cyclin B1 (CCNB1) and cyclin dependent kinase 1 (CDC2). MPF activity is regulated by the expression level of CCNB1, phosphorylation of CDC2, and their germinal vesicle localization. In addition to CCNB1, cyclin O (CCNO) is highly expressed in oocytes, but its biological functions are still not clear. By employing siRNA microinjection of germinal vesicle (GV) stage oocytes, we found that Ccno knock-down inhibited CDC2(Tyr15) dephosphorylation and arrested oocytes at the GV stage. To rescue meiotic resumption, Cdc25b and Ccnb1 were overexpressed in the Ccno knock-down oocytes. Unexpectedly, we found that Ccno knock-down did not affect CDC25B entry into the GV, and overexpression of CDC25B was not able to rescue resumption of oocyte meiosis. However, GV breakdown (GVBD) was significantly increased after overexpression of Ccnb1 in Ccno knock-down oocytes, indicating that GVBD block caused by cyclin O knock-down can be rescued by cyclin B1 overexpression. We thus conclude that cyclin O, as an upstream regulator of MPF, plays an important role in oocyte meiotic resumption in mouse oocytes.