Methylation Of H4 By SETD6 And Its Impact On Breast Cancer Cell Proliferation

Histone proteins are the critical component of the nucleosome and are subject to lysine methylation which is important in the regulation of chromatin structure and epigenetic processes.Unlike histone H3,the only methylation site has been found of H4 is H4K20 until now.Accumulating evidence has revealed that lysine methyltransferases(KMT)play an important role in many cellular functions.Whereas the catalytic activity and substrate specificity of large numbers of KMT has not been found.It has been reported that H2 AZ is monomethylated at lysine 7 by the lysine methyltransferase SETD6.In our previous study,we found that lysine methyltransferase SETD6 monomethylated the lysine 207 and 325 residues of WDR5.The lysine methylation of WDR5 increases the level of H3K4me3 and promotes proliferation and migration of breast cancer cell.But it is not clear that whether SETD6 can methylate other histones.Our data reveal that SETD6 can catalyze the methylation of histone H4.Then we synthesized the peptide which is the first 30 amino acid sequences of the C-terminus of histone H4.The autoradiography experiment showed that SETD6 can methylate this peptide.It suggested that the methylated site is located on the first 30 amino acids of H4.We then performed mass spectrometry analysis of the peptide and found that H4K16 is a new H4 monomethylation site.Following studies found that H4K16me1 levels are higher in MCF7 and MDA-MB-231 cells with higher expression of SETD6,and lower levels of H4K16me1 in MCF-10 A cells with lower SETD6 expression.H4K16me1 levels increases with overexpression of SETD6 in MCF-10 A cells,whereas H4K16me1 levels decrease after knockdown of SETD6 in MCF7 cells.The proliferation of breast cancer cell will be attenuated if SETD6 decreases.And the depletion of SETD6 is likely to induce a block in the S-phase by flow cytometry.This work provides new evidence for research of the biological functions of SETD6.