occur. Serine phosphorylation sites have been identified on H2A. Threonine O-GlcNAc has also been identified on H2A. Large differences exist between the modified residues of H2A variants. For example, H2ABbd lacks modified residues that exist in H2A. The differences in modification change the function of H2ABbd compared to H2A. As previously mentioned, variant H2AX was found to function in DNA repair. This function is dependent upon the phosphorylation of H2AX C-terminal. Once H2AX becomes phosphorylated, it can function in DNA repair. The H2A.X variant differs from H2A through modification. The C-terminal of H2A.X contains an additional motif compared to H2A. The motif that is added is Ser-Gln-(Glu/Asp)- (hydrophobic residue). The motif becomes heavily phosphorylated at the serine residue; if this phosphorylation occurs the variant becomes γH2A.X. Phosphorylation occurs due to dsDNA breaks. Modification on histone proteins can sometimes result in a change in function. Different H2A variants were exploited to have different functions, genetic sequences, and modifications. See also Histone code Chromatin Nucleosome References External links Nextbio Proteins