Mitotic Histone H3 Phosphorylation by Vaccinia-Related Kinase 1 in Mammalian Cells

Abstract

Mitotic chromatin condensation is essential for cell division in eukaryotes. Posttranslational modification of the N-terminal tail of histone proteins, particularly by phosphorylation by mitotic histone kinases, may facilitate this process. In mammals, aurora B is believed to be the mitotic histone H3 Ser10 kinase; however, it is not sufficient to phosphorylate H3 Ser10 with aurora B alone. We show that histone H3 is phosphorylated by vaccinia-related kinase 1 (VRK1). Direct phosphorylation of Thr3 and Ser10 in H3 by VRK1 both in vitro and in vivo was observed. Loss of VRK1 activity was associated with a marked decrease in H3 phosphorylation during mitosis. Phosphorylation of Ser10 by VRK1 is similar to that by aurora B. Moreover, expression and chromatin localization of VRK1 depended on the cell cycle phase. Overexpression of VRK1 resulted in a dramatic condensation of nuclei. Our findings collectively support a role of VRK1 as a novel mitotic histone H3 kinase in mammals.Chromatin congregates to chromosomes during mitosis to facilitate the even segregation of genetic information to two daughter cells. In nucleosomes, the combinational modification of histone tails, the so-called "histone code," controls chromatintemplated processes from gene expression to cell fate decision (20,30). Phosphorylation of the N-terminal tail of histone H3 may be responsible for chromatin condensation (21). During mitosis, the N-terminal tail of histone H3 is phosphorylated at several residues, including Thr3 (5, 36), Ser10 (3,7,17,18), Thr11 (37), and Ser28 (12). A correlation between histone H3 Ser10 phosphorylation and chromatin condensation in Aspergillus nidulans (6) and Tetrahymena thermophila (47) is well established. However, in other species, condensation is not accomplished simply by Ser10 phosphorylation, and additional phosphorylation or modification of histone tails is required (21).A number of studies have shown that members of the aurora kinase family are responsible for phosphorylation of histone H3 (3,7,17,18). Mammals contain three isotypes of aurora kinase designated aurora A, B, and C (11). Among these, aurora B is a strong candidate phosphorylator of Ser10 in histone H3 as is evident from data obtained with hesperadin, the aurora B inhibitor (14), which suppressed Ser10 phosphorylation during mitosis (7, 17). However, residual Ser10 phosphorylation was detected, even upon depletion of aurora B in cells, suggesting the presence of an additional histone H3 kinase (29).NIMA (never in mitosis), the histone H3 Ser10 kinase in Aspergillus nidulans (6, 34), triggers chromatin condensation in cells arrested at the interphase (28). In mammals, Nercc1, the functional ortholog of NIMA, was found to be phosphorylating histone H3 (39). Nucleosomal histone kinase 1 (NHK1) from Drosophila melanogaster is the kinase shown to phosphorylate histone protein in chromatin as a substrate. NHK1 phosphorylated H2A at Thr119 in chromatin but not with free histone as the substrate (1). Recent studies showed that NHK1 participates in mit...

Phosphorylation of human enhancer of filamentation (HEF1) on serine 369 induces its proteasomal degradation

“…This augmentation remains unexplained; although it is possible that the over accumulation of p105HEF1 might result in increased phosphorylation. Alternatively, there are examples of proteins in which a single residue is the target of different kinases [41,42]. So we can not exclude that other kinase(s) phosphorylate HEF1 on ser-369 but also on another residue leading to an HEF1 isoform that would be less sensitive to degradation and would be part of the p115 band.…”

Histone H3 phosphorylation: Universal code or lineage specific dialects?

“…In metazoa, H3T11 is likely phosphorylated by the Dlk/ZIP kinase, 15 a member of the death associated protein kinase family that lacks true orthologs in plants. 16 H3T3 and H3S10 also seem to be phosphorylated by Vaccinia-Related Kinase 1 (VRK1), 17 another metazoa-specific protein (Fig. 1).…”

“…14,18,19 This pattern of phosphorylation and other analyses suggested that H3S10ph and H3S28ph might play a role in chromosome condensation. 8,17,20 Phosphorylation of H3T3 initially overlaps with that of H3S10ph but, at metaphase, H3T3ph is more intensely concentrated in the central region of the metaphase plate. 14,19 In metazoa, H3T3ph has been implicated in metaphase chromosome alignment and centromeric cohesion, 8,14 although given the similarities with the H3S10ph distribution, it might also function in chromosome condensation.…”

VRK1 interacts with p53 forming a basal complex that is activated by UV‐induced DNA damage

“…VRK1, the most abundant Ser-Thr kinase in nuclei [23], is a nucleosomal/chromatin kinase that can form complexes and phosphorylate several transcription factors [24][25][26], histones [18,[27][28][29] and other chromatin proteins [30,31]. Moreover, VRK1 kinase activity can also be regulated by these proteins interactions, including those with histones [28][29][30].…”

“…VRK1 is required for G0 exit, behaving like an early gene such as MYC and FOS [36]. VRK1 is also required for phosphorylation of histone H3 and chromatin compaction late in mitosis [27]. Moreover, VRK1 positively correlates with the proliferation phenotype in human head and neck [37] and lung cancers [34,38], and in breast cancer xenographs it also affects proliferation [39].…”