Abstract
Positive transcription elongation factor b (P-TEFb) is a RNA polymerase II carboxyl-terminal domain (Pol II CTD) kinase that phosphorylates Ser2 of the CTD and promotes the elongation phase of transcription. Despite the fact that P-TEFb has role in many cellular processes, the role of this kinase complex remains to be understood in mammalian early developmental events. In this study, using immunocytochemical analyses, we found that the P-TEFb components, CDK9, Cyclin T1 and Cyclin T2 were localized to nuclear speckles, as well as in nucleolar-like bodies in pig germinal vesicle oocytes. Using nascent RNA labeling and small molecule inhibitors, we showed that inhibition of CDK9 activity abolished the transcription of GV oocytes globally. Moreover, using fluorescence in situ hybridization, in absence of CDK9 kinase activity the production of ribosomal RNAs was impaired. We also presented the evidences indicating that P-TEFb kinase activity is essential for resumption of oocyte meiosis and embryo development. Treatment with CDK9 inhibitors resulted in germinal vesicle arrest in maturing oocytes in vitro. Inhibition of CDK9 kinase activity did not interfere with in vitro fertilization and pronuclear formation. However, when in vitro produced zygotes were treated with CDK9 inhibitors, their development beyond the 4-cell stage was impaired. In these embryos, inhibition of CDK9 abrogated global transcriptional activity and rRNA production. Collectively, our data suggested that P-TEFb kinase activity is crucial for oocyte maturation, embryo development and regulation of RNA transcription in pig.
Highlights
Embryonic genome activation is a highly regulated process by which an embryo begins to produce its own gene products from its newly formed genome
Using specific antibodies, we observed that cyclin-dependent kinase 9 (CDK9), Cyclin T1 and Cyclin T2 are present and dominate the GVs of oocytes obtained from pig antral follicles (Fig 1A)
Similar to what we observed in mice oocytes, CDK9 and Cyclin T1 exhibited large round bodies scattered throughout the GVs of pig oocytes with open chromatin (NSN and partly NSN)
Summary
Embryonic genome activation is a highly regulated process by which an embryo begins to produce its own gene products from its newly formed genome. Before the embryonic genome is activated, the embryo is transcriptionally inactive and is dependent on the factors already provided by the oocyte. These factors (mainly proteins and mRNAs) are produced during the course of oocyte growth until the oocyte becomes competent for resumption of meiosis. Before the oocytes become competent to maturation process, the oocyte genome undergoes changes. CDK9 Activity on Porcine Oocyte and Embryo Development role of this author is articulated in the ‘author contributions’ section
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
