Fission yeast Hrp1, a chromodomain ATPase, is required for proper chromosome segregation and its overexpression interferes with chromatin condensation

Hrp1 of Schizosaccharomyces pombe is a member of the CHD protein family, ch aracterized by a chromo-domain, a Myb-like telobox-related DNA-binding doma in and a SNF2-related helicase/ATPase domain. CHD proteins are thought to b e required for modification of the chromatin structure in transcription, bu t the exact roles of CHD proteins are not known, Here we examine the sub-ce llular localization and biochemical activity of Hrp1 and the phenotypes of hrp1 Delta and Hrp1-overexpressing strains. Fluorescence microscopy reveale d that Hrp1 protein is targeted to the nucleus, We found that Hrp1 exhibite d DNA-dependent ATPase activity, stimulated by both single- and double-stra nded DNA, Overexpression of Hrp1 caused slow cell growth accompanied by def ective chromosome condensation in anaphase resulting in a 'cut' (cell untim ely torn) phenotype and chromosome loss. The hrp1 Delta mutation also cause d abnormal anaphase and mini-chromosome loss phenotypes. Electron micrograp hs demonstrated that aberrantly shaped nucleoli appeared in Hrp1-overexpres sing cells. Therefore, these results suggest that Hrp1 may play a role in m itotic chromosome segregation and maintenance of chromatin structure by uti lizing the energy from ATP hydrolysis.