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P‐TEFb Regulates Oocyte Maturation and Embryonic Genome Activation by Pol II CTD Phosphorylation and Ribosomal RNA Processing in Mammals
Author(s) -
Jin Dong Il,
Oqani Reza K,
Lin Tao,
Lee Jae Eun,
Kim So Yeon
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.597.1
Subject(s) - p tefb , rna polymerase ii , biology , germinal vesicle , microbiology and biotechnology , cyclin dependent kinase 9 , transcription (linguistics) , oocyte , kinase , embryo , gene expression , genetics , protein kinase a , gene , cyclin dependent kinase 2 , promoter , linguistics , philosophy
Positive transcription elongation factor b (P‐TEFb) is an essential RNA polymerase II carboxyl‐terminal domain (Pol II CTD) kinase that phosphorylates Ser2 of the CTD and promotes the elongation phase of transcription. In addition to its role in mRNA production, P‐TEFb is involved in many other cellular events such as DNA damage response and histone modification. Also, recent studies have shown that disruption of P‐TEFb or its homologue in yeast Bur1, impairs ribosomal RNA (rRNA) processing. Here we have investigated the importance of CDK9 kinase subunit of P‐TEFb in early mouse and pig embryo development. We found that CDK9 and its regulatory partner Cyclin T1 are localized into germinal vesicles of oocytes and also embryonic nuclei throughout the preimplantation development. Also, these proteins are co‐localized with nuclear speckles as well as with nucleolar components in oocytes and embryos. Disruption of CDK9 activity by various small molecule inhibitors resulted in defective oocyte maturation and also developmental arrest at the time of embryonic genome activation. Immunolabeling analysis showed that inhibition of CDK9 declines Pol II CTD phosphorylation and nuclear transcription globally in oocyte and embryo. Both nuclear and nucleolar nascent RNAs were negatively affected by CDK9 inhibitors. Also, using RNA fluorescence in situ hybridization for nascent RNA analysis, it was found that inhibition of CDK9 disrupted nucleolar integrity and impairs 28S rRNA production dramatically. Collectively, our data show that P‐TEFb is an important role in both resumption of meiosis and embryonic genome activation, and moreover, CDK9 could be involved in both Pol I‐ and Pol II‐dependent transcription in early mammalian development.