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General Comment |
NCBI Summary:
This gene encodes a member of the Polycomb-group (PcG) family. PcG family members form multimeric protein complexes, which are involved in maintaining the transcriptional repressive state of genes over successive cell generations. This protein interacts with enhancer of zeste 2, the cytoplasmic tail of integrin beta7, immunodeficiency virus type 1 (HIV-1) MA protein, and histone deacetylase proteins. This protein mediates repression of gene activity through histone deacetylation, and may act as a specific regulator of integrin function. Two transcript variants encoding distinct isoforms have been identified for this gene.
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Comment |
The polycomb group protein EED varies in its ability to access the nucleus in porcine oocytes and cleavage stage embryos. Foust KB et al. Chromatin-modifying complexes serve essential functions during mammalian embryonic development. Polycomb group proteins EED, SUZ12, and EZH2 have been shown to mediate methylation of the lysine 27 residue of histone protein H3 (H3K27), an epigenetic mark that is linked with transcriptional repression. H3K27 trimethylation has been shown to be present on chromatin in mature porcine oocytes, pronuclear and 2-cell stage embryos, with H3K27 trimethylation decreasing at the 4-cell stage and not detectable in blastocyst stage embryos. The goals of this study were to determine the intracellular localization of the polycomb group protein EED in porcine oocytes and cleavage stage porcine embryos produced by in vitro fertilization and to determine the binding abilities of karyopherin a subtypes toward EED. Our results revealed that EED had a strong nuclear localization in 4-cell and blastocyst stage embryos and a strong perinuclear staining in GV-stage oocytes; EED was not detectable in the nuclei of pronuclear or 2-cell stage embryos. An in vitro binding assay was performed to assess the ability of EED to interact with a series of karyopherin a subtypes; results from this experiment revealed that EED can interact with several karyopherin a subtypes, but with varying degrees of affinity. Together these data indicate that EED displays a dynamic change in intracellular localization in progression from immature oocyte to cleavage stage embryo and that EED possess differing in vitro binding affinities toward individual karyopherin a subtypes, which may in part regulate the nuclear access of EED during this window of development.
Expression of Polycomb-group genes in human ovarian follicles, oocytes and preimplantation embryos Hinkins M, et al .
Mammalian oocytes possess unique properties with respect to their ability to regulate and reprogram chromatin structure and epigenetic information. Proteins containing the conserved chromodomain motif that is common to the Polycomb-group (Pc-G) proteins and the heterochromatin-associated protein HP1, play essential roles in these processes and more specifically, in X-chromosome inactivation in female zygotes and extra-embryonic tissues and in the regulation of genomic imprinting. To characterize the potential role of these proteins in the regulation of epigenetic events during early human development, we utilized a degenerate PCR priming assay to assess the expression of mRNAs of chromodomain proteins in cDNA samples derived from the human female germline and preimplantation embryos. Expression of mRNAs of HP1 genes was observed in ovarian follicles, (HP1 (HSalpha), HP1 (HSbeta), HP1 (HSgamma)), mature oocytes (HP1 (HSalpha), HP1 (HSbeta)), cleavage stage preimplantation embryos (HP1 (HSalpha), HP1 (HSbeta), HP1 (HSgamma)) and blastocysts (HP1 (HSalpha), HP1 (HSgamma)). Transcripts for three Pc-G genes, which are essential for early mammalian development (Yin Yang 1 (YY1), Enhancer of Zeste-2 (EZH2) and Embryonic Ectoderm Development (EED)) and that are essential for the regulation of X-inactivation and certain imprinted genes (EED) were revealed by gene-specific-PCR expression analysis of human ovarian follicles, oocytes and preimplantation embryos. YY1 and EZH2 transcripts were additionally detected in metaphase II oocytes.
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