Reversal of Ubiquitylation: The Role of USP7 and UBP64 in Drosophila Development

The genetic information of eukaryotes is organised in a nucleoprotein complex called chromatin. The fundamental repeating unit of chromatin is nucleosome in which 146 bp of DNA is wrapped around octamer of core histone proteins H2A, H2B, H3 and H4. Histone H1 (linker histone) associates with DNA between two nucleosomes. Core histones are highly conserved proteins among all eukaryotes. The N-terminus of the core histones extends outwards from the nucleosome and is flexible in nature whereas the globular C-terminus forms the scaffold of the nucleosome (Fischle et al., 2003). Nature has evolved mechanisms to dynamically alter chromatin structure like chromatin remodelling by ATP dependent chromatin remodellers, covalent histone modifications, and replacement of histone proteins by their respective variants.