Dnmt3b, de novo DNA methyltransferase, interacts with SUMO-1 and Ubc9 through its N-terminal region and is subject to modification by SUMO-1

Abstract

Dnmt3b, a DNA methyltransferase, is essential for mammalian development potentially through its transcription repression activity. To comprehend the underlying regulatory mechanism of Dnmt3b, we isolated small ubiquitin-like modifier 1 (SUMO-1) and Ubc9 as Dnmt3b-interacting proteins using yeast two-hybrid screens. Deletion analysis demonstrated that Dnmt3b interacts with SUMO-1 and Ubc9 at its N-terminal region. We observed that Dnmt3b is modified by SUMO-1 and colocalizes with SUMO-1 in vivo. Dnmt3b is also known as transcription repressor. According to our study, sumoylation of Dnmt3b relieves transcriptional repression fuction of Dnmt3b. These results suggest that sumoylation may constitute a regulation mechanism of Dnmt3b in vivo. After two-hybrid screening, we isolated additionally several proteins involved in DNA repair. To investigate whether Dnmt3b is related to DNA repair, we observed the mRNA level of Dnmt3b after UV treatment. The mRNA level of Dnmt3b decreased gradually after UV treatment.