First Detailed Analysis of a Relatively Deep, Low Mass-ratio Contact Binary:ATO J108.6991+27.8306

We present the first detailed photometric analysis of ATO J108.6991+27.8306(hereinafter as J108).The shortperiod close binary J108 was observed by the Nanshan 1 m Wide Field Telescope of the Xinjiang Astronomical Observatory.The obtained BVRI-band light curves were used to determine the photometric solution by using the 2003 version of the Wilson-Devinney code.J108 is a typical deep(f>50%),low mass ratio(q<0.25)overcontact binary system with a mass ratio of q=0.1501 and a fill-out factor of f=50.1%,suggesting that it is in the late evolutionary stage of contact binary systems.We found the target to be a W-type W UMa binary and provided evidence for the presence of starspots on both components.From the temperature-luminosity diagram,the main component is the evolved main sequence star with an evolutionary age of about 7.94 Gyr.

Metastasis-related methyltransferase 1(Merml)represses the methyltransferase activity of Dnmt3a and facilitates RNA polymerase I transcriptional elongation

Stimulatory regulators for DNA methyltransferase activity,such as Dnmt3L and some Dnmt3b isoforms,affect DNA methylation patterns,thereby maintaining gene body methylation and maternal methylation imprinting,as well as the methylation landscape of pluripotent cells.Here we show that metastasis-related methyltransferase 1(Merm1),a protein deleted in individuals with Williams-Beuren syndrome,acts as a repressive regulator of Dnmt3a.Merm1 interacts with Dnmt3a and represses its methyltransferase activity with the requirement of the binding motif for S-adenosyl-L-methionine.Functional analysis of gene regulation revealed that Merm1 is capable of maintaining hypomethylated rRNA gene bodies and co-localizes with RNA polymerase I in the nucleolus.Dnmt3a recruits Merml,and in return,Merml ensures the binding of Dnmt3a to hypomethylated gene bodies.Such interplay between Dnmt3a and Merml facilitates transcriptional elongation by RNA polymerase I.Our findings reveal a repressive factor for Dnmt3a and uncover a molecular mechanism underlying transcriptional elongation of rRNA genes.