Kim Sung-Hak, Park Jinah, Choi Moon-Chang, Kim Hwang-Phill, Park Jung-Hyun, Jung Yeonjoo, Lee Ju-Hee, Oh Do-Youn, Im Seock-Ah, Bang Yung-Jue, Kim Tae-You
National Research Laboratory for Cancer Epigenetics, Cancer Research Institute, Seoul, Republic of Korea.
Biochem Biophys Res Commun. 2007 Apr 6;355(2):318-23. doi: 10.1016/j.bbrc.2007.01.187. Epub 2007 Feb 8.
DNA methyltransferases (DNMT) 3B is a de novo DNMT that represses transcription independent of DNMT activity. In order to gain a better insight into DNMT3B-mediated transcriptional repression, we performed a yeast two-hybrid analysis using DNMT3B as a bait. Of the various binding candidates, ZHX1, a member of zinc-finger and homeobox protein, was found to interact with DNMT3B in vivo and in vitro. N-terminal PWWP domain of DNMT3B was required for its interaction with homeobox motifs of ZHX1. ZHX1 contains nuclear localization signal at C-terminal homeobox motif, and both ZHX1 and DNMT3B were co-localized in nucleus. Furthermore, we found that ZHX1 enhanced the transcriptional repression mediated by DNMT3B when DNMT3B is directly targeted to DNA. These results showed for the first the direct linkage between DNMT and zinc-fingers homeoboxes protein, leading to enhanced gene silencing by DNMT3B.
DNA甲基转移酶（DNMT）3B是一种从头甲基转移酶，可独立于DNMT活性抑制转录。为了更好地了解DNMT3B介导的转录抑制作用，我们以DNMT3B为诱饵进行了酵母双杂交分析。在各种结合候选物中，发现锌指和同源框蛋白成员ZHX1在体内和体外均与DNMT3B相互作用。DNMT3B的N端PWWP结构域是其与ZHX1的同源框基序相互作用所必需的。ZHX1在C端同源框基序处含有核定位信号，且ZHX1和DNMT3B均共定位于细胞核中。此外，我们发现当DNMT3B直接靶向DNA时，ZHX1可增强DNMT3B介导的转录抑制作用。这些结果首次表明了DNMT与锌指同源框蛋白之间存在直接联系，从而导致DNMT3B增强基因沉默。
