Structural and biochemical studies on chromatin regulation by CHD7

Abstract

CHD7 which is ATP dependent chromatin remodeler regulates gene expression by controlling chromatin structure. Mutations in CHD7 are the major cause of CHARGE syndrome. But it is unknown which domain in CHD7 contacts which portion of the nucleosome and how it is linked to remodeling activity. Also, the substrate specificity and molecular mechanism of CHD7 are poorly understood. Here, we performed integrative biophysical analysis on CHD7 chromatin remodeler using crosslinking-mass spectrometry (XL-MS), cryo-Electron Microscopy (cryo-EM) and single-molecule FRET. I noticed that the N-terminal region of CHD7 plays a critical role in nucleosome binding as well as remodeling. To characterize this further, I determined the cryo-EM structure of the N-Chromo (CRD) of CHD7 bound to nucleosome. Interestingly, N-CRD contacts the face of the histone octamer and it seems that N-CRD interacts with the acidic patch of nucleosome. Further, by single-molecule FRET and biochemical analysis, we show that the acidic patch is an important epitope for the remodeling of CHD7. In addition, I propose arginine cluster region present in N_CRD that is expected to interact with the acidic patch and the mutations in the arginine cluster region result in slow or highly-fluctuating remodeling activity. Overall, our study reveals the molecular basis of chromatin remodeling by CHD7 and proposes a new regulatory region important for remodeling