Authors: Meng Xia, Hui He, Ying Wang, Minxi Liu, Tao Zhou, Min Lin, Zuomin Zhou, Ran Huo, Qi Zhou and Jiahao Sha

Meng Xia

State Key Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing, China

Hui He

State Key Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing, China

Ying Wang

State Key Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing, China

Minxi Liu

State Key Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing, China

Tao Zhou

State Key Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing, China

Min Lin

State Key Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing, China

Zuomin Zhou

State Key Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing, China

Ran Huo

Corresponding author: huoran@njmu.edu.cn
State Key Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing, China

Qi Zhou

Corresponding author: qzhou@ioz.ac.cn
State Key Laboratory of Reproductive Biology; Institute of Zoology; The Chinese Academy of Science; Beijing, China

Jiahao Sha

State Key Laboratory of Reproductive Medicine; Department of Histology and Embryology; Nanjing Medical University; Nanjing, China

Abstract:
Global transcriptional silencing in fully grown oocytes is a critical event during mammalian oogenesis. However, how this event is regulated remains elusive. Here, we provide evidence that poly(rC)-binding protein 1 (PCBP1), a protein found by us previously to be present in metaphase II (MII) mouse oocytes, participates in maintenance of the transcriptionally silent state in fully grown mouse oocytes. Knocking down Pcbp1 by microinjection of its specific siRNAs into fully grown germinal vesicle (GV) oocytes resulted in remarkable changes in their transcriptional state, including the disequilibrium between the number of oocytes with an NSN (non-surrounded nucleolus) and those with a SN (surrounded nucleolus), and obvious transcriptional reactiviation in oocytes with a SN configuration as evidenced by BrUTP incorporation assay and immunofluorescent labeling of phosphorylated RNA polymerase II CTD and trimethylated H3 lysine 4, markers for active transcription. Furthermore, in a comprehensive microarray analysis of the preovulatory oocyte transcriptome, an incredible number of nearly 4,000 transcripts were upregulated in the Pcbp1 knockdown groups. These data indicate that lack of the function of PCBP1 disrupts the quiescent status of transcription in the fully grown oocytes, and hence supporting a role of this protein in the regulation of global transcriptional silcencing in fully grown mouse oocytes.

Received: February 3, 2012; Accepted: June 19, 2012

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