Chromatin remodelers: We are the drivers!!

Abstract

Chromatin is a highly dynamic structure that imparts structural organization to the genome and regulates the gene expression underneath. The decade long research in deciphering the significance of epigenetics in maintaining cellular integrity has embarked the focus on chromatin remodeling enzymes. These drivers have been categorized as readers, writers and erasers with each having significance of their own. Largely, on the basis of structure, ATP dependent chromatin remodelers have been grouped into 4 families; SWI/SNF, ISWI, IN080 and CHD. It is still unclear to what degree these enzymes are swayed by local DNA sequences when shifting a nucleosome to different positions. The ability of regulating active and repressive transcriptional state via open and close chromatin architecture has been well studied however, the significance of chromatin remodelers in regulating transcription at each step i.e. initiation, elongation and termination require further attention. The authors have highlighted the significance and role of different chromatin remodelers in transcription, DNA repair and histone variant deposition.

Keywords: Chromatin remodelers; histone variants; transcription.

Figure 1.

Diagrammatic representation of chromatin remodeler family highlighting the conserved domain with each family member. The DEX and HELICc domains are conserved throughout the family. However, HAND, SANT and SLIDE domains are specific to ISWI family, whereas BROMO domain distinguishes the SWI/SNF family. The presence of CHROMO domains is characteristic of CHD family.

Figure 2.

Schematic representation of subfamilies of CHD family of chromatin remodelers. The CHD family is divided into 3 subfamilies, each subfamily is designated with specific set of domains (PHD, SANT, BRK).

Figure 3.

Chromatin remodeler of CHD family and their association with different stages of transcription. CHD7 and CHD8 subfamily in association with other cofactors trigger the transcription initiation and elongation at the enhancer and promoter region of the gene, where as in yCHD1 has been shown to involve in transcription termination.