Transcription, DNA damage and beyond: the roles of histone ubiquitination and deubiquitination

Myriad covalent post-translational modifications of histones have been demonstrated to play crucial roles in regulating gene transcription, gene repression, DNA damage and repair, and beyond. It has been long known that these modifications are often dynamic, such as histone ubiquitination and deubiquitination, and the processes through adding and/or removing these modified marks catalyzed by various classes of enzymes commonly influence many important physiological functions. In recent few years, studies on histone ubiquitination re-garners much attention arising from lots of new exciting findings emerged. Several important histone ubiquitination sites have been mapped in different organisms. In addition, the identification and characterization of numerous ubiquitin modifying enzymes, especially ligases and deubiquitinases, have facilitated the progress in understanding the roles of histone ubiquitination/deubiquitination events. Of particular interest, histone ubiquitination interplays with many other chromatin modifications, namely "crosstalk", which contributes to a variety of cellular events. In this review, I summarize the enzymes and factors involved in regulating the attachment and removal of ubiquitin from histones, and focus on what essential roles this modification plays. I also present new evidence that links histone ubiquitination with other histone modifications, which comprises an intricate crosstalk network.