Histone H2A T120 Phosphorylation Promotes Oncogenic Transformation via Upregulation of Cyclin D1

Abstract

How deregulation of chromatin modifiers causes malignancies is of general interest. Here, we show that histone H2A T120 is phosphorylated in human cancer cell lines and demonstrate that this phosphorylation is catalyzed by hVRK1. Cyclin D1 was one of ten genes downregulated upon VRK1 knockdown in two different cell lines and showed loss of H2A T120 phosphorylation and increased H2A K119 ubiquitylation of its promoter region, resulting in impaired cell growth. In vitro, H2A T120 phosphorylation and H2A K119 ubiquitylation are mutually inhibitory, suggesting that histone phosphorylation indirectly activates chromatin. Furthermore, expression of a phosphomimetic H2A T120D increased H3 K4 methylation. Finally, both VRK1 and the H2A T120D mutant histone transformed NIH/3T3 cells. These results suggest that histone H2A T120 phosphorylation by hVRK1 causes inappropriate gene expression, including upregulated cyclin D1, which promotes oncogenic transformation.

Defects in centromeric/pericentromeric histone H2A T120 phosphorylation by hBUB1 cause chromosome missegregation producing multinucleated cells

“…The H2A T120D mutation behaved like T120 phosphorylation and transformed NIH3T3 cells. Thus, we suggest that inappropriate bulk H2A T120 hyperphosphorylation affects the transcription of oncogenes such as Cyclin D1, resulting in carcinogenesis (Aihara et al., ). However, Bub1 was identified as a mitotic kinase in yeast and was found to phosphorylate H2A S121 (equivalent to T120 in mammals) (Kawashima et al., ).…”

“…We reported that this hyperphosphorylation of H2A T120 is catalyzed by hVRK1. In addition to this inappropriate bulk hyperphosphorylation, VRK1 phosphorylates nucleosomal H2A T120 around the gene promoter region (Aihara et al., ). In this study, we confirmed that bulk H2A T120 phosphorylation, which is enhanced during M phase in HeLa cells, is catalyzed by hBUB1, as it is reduced by knockdown using either of two siRNA oligonucleotides, siBUB1‐1 or siBUB1‐2 (Figure d).…”

“…In addition to this inappropriate bulk hyperphosphorylation, VRK1 phosphorylates nucleosomal H2A T120 around the gene promoter region in all cell lines tested (Aihara et al., ). VRK1 catalyzed bulk H2A T120 phosphorylation, which is inappropriately increased irrespective of the cell cycle phase in HT1080 and MDA‐MB‐231 cells but does not affect H2A T120 phosphorylation enhancement during M phase in HeLa cells (Aihara et al., ). In addition, we showed that H2A T120 phosphorylation by VRK1 around the Cyclin D1 promoter region plays a role in carcinogenesis.…”

“…The fact that the C‐terminal end of histone H2A and the N‐terminal end of histone H3 contain the linker DNA entry and exit points suggests their functional importance. We previously found that nucleosomal histone kinase‐1 (NHK1) is a histone H2A kinase (Aihara et al., ), and we recently determined that hVRK1, a human homologue of dNHK1, phosphorylates nucleosomal H2A T120 around the promoter region of genes such as CCND1 and regulates transcription (Aihara et al., ), as the neighboring histone H2A lysine 119 is a well‐known ubiquitylation site that is closely associated with transcriptional repression (Aihara et al., ; Wang et al., ). Because the substrate specificity of NHK1 is very tight, it is expected that there is a cross talk between histone H2A lysine 119 ubiquitylation and threonine 120 phosphorylation.…”

VRK1 and AURKB form a complex that cross inhibit their kinase activity and the phosphorylation of histone H3 in the progression of mitosis

“…Thus, it is very likely that the pattern of histone H3 phosphorylation depends on the position of the individual histone H3 molecule and the kinases present at these locations. VRK1 phosphorylates both H3–Thr3 and H2A–Thr120 [48]. Phosphorylated H3–Thr3 is recognized by survivin [25], whose gene expression is also activated by VRK1 [23].…”