Identification of epigenetic protein complexes and functional analyses

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1.We have isolated a protein, by yeast two-hybrid methods, which specifically binds to human SNF/SWI components hSNF2a/hbrm and hSNF2b/BRG-1. The protein TMF has been reported as a factor that associates and cooperates with androgen receptor. TMF was found to localize in Golgi apparatus. (Mori et al.)2.We have constructed knock-out mice lacking the G9a gene whose product has methylation activity to lysine 9 of histone H3 (H3K9). The mice show lethality in early development phase and ES cells lacking both alleles of G9a show evidently decreased level of H3K9 methylation of euchromatin region. In vivo transient expression experiments indicated that G9a could play a role in transcription repression. (Tachibana et al.)3.We have isolated two mammalian polycomb complexes and identified new components. One of the complexes showed methyltransferase activity to histone H3 lysine 27. The other complex had specific binding activity to H3K27. These mutually coordinate activities explain the similarity in genetical phenotypes between these two polycomb complexes and reinforce their importance in transcriptional repression.