Covalent modifications of histone tails have fundamental roles in chromatin structure and transcriptional activity of a target locus. One of such modifications, Methylation at Lysine 9 of histone H3 (H3-K9) causes several epigenetic phenomena including heterochromatin formation, transcriptional regulation and DNA methylation. Setdb1, H3-K9 specific histone methyltransferase, functions in gene silencing, heterochromatin formation and essential role for early development. Here, we demonstrate that Setdb1 associates with promyelocytic leukemia (Pml) protein from the early stage of mouse development and is a constitutive member of PML nuclear bodies (PML-NBs) that have been linked to many cellular processes such as apoptosis, DNA damage responses, and transcriptional regulation. Immunostaining of mouse blastocyst showed that Setdb1 and Pml signals were scattered in nucleus as a few speckles and microinjected Pmlmyc signals colocalize with Setdb1 signals. This colocalization was observed in mEF and the punctate signals of Setdb1 were observed to be present in every nucleus of mEFs and dividing cells with condensed chromosomes. Arsenic treatment, which induces Pml degradation, also caused Setdb1 signals to disappear. Setdb1 knockdown resulted in disassembly of PML-NBs and immunoprecipitation results demonstrated physical interactions between Setdb1 and Pml. These data suggest that Setdb1 was associated in PML-NB and Setdb1 has important function in maintenance of PML-NB structure.

• Sunwha Cho(Regenerative Medicine Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB))
• Jung Sun Park(Regenerative Medicine Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB))
• Yong-Kook Kang(Regenerative Medicine Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB))