Histone phosphorylation and mitosis

Phosphorylation of HI during mitosis is catalyzed by the cyclin B-Cdc2 kinase, a tightly regulated enzyme [25,26]. In Tetrahymena mitotically dividing nuclei, cyclic-AMP dependent kinase (PKA) or PKA-like kinase phosphorylates HI [27,28]. Protein phosphatase 1 dephosphorylates the phosphorylated HI [29]. 

H3 differs from the other core histones in that it is phosphorylated to a greater extent during mitosis than during other parts of the cell cycle [4,30] (Fig. 4). During 

The centromeric-specific histone H3-like variant, CENP-A, that is present in all eukaryotes is phosphorylated by aurora B at Ser-7 and dephosphosphorylated by 

G2/M hAurora B (AIM-2) yAuora/IP11p cAurora/AIR-2 aNIMA I Aurora B (AIM-2) yAuora/IPIIp cAurora/AIR-2 1 

cerevisiae aurora/IPllp, C. elegans aurora/AIR-2, and mammalian aurora B (also called AIM-1) phosphorylate H3 at Ser-10 and Ser-28 during mitosis [39 1] (Fig. 5). Protein phosphatase 1 removes the phosphate at these sites [39,42]. INCENP is bound to aurora B and is essential for the proper targeting of aurora B on the chromosomes [43-45]. INCENP and aurora B (AIM-1) are overexpressed in a variety of human cancers, including colorectal cancer [43,46]. Overexpression of aurora B (AIM-1) in CHE diploid fibroblasts leads to chromosomal instability, suggesting that aurora B overexpression may play a role in carcinogenesis [46]. INCENP/aurora B and H3 phosphorylation appear to be involved in assembly of mitotic chromosomes, but not mitotic chromosome compaction [44,47]. 

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