Abstract
We identified nuclei or chromosome-specific proteins by visual screening of Arabidopsis transformants using random GFP-cDNA fusions. A novel nucleoplasm-specific protein, AHL1, contains an AT-hook motif and a PPC (plants and prokaryotes conserved) domain that is indispensable for the nuclear localization. The PPC domain is not found in the animal kingdom but in Bacteria, Archaea and the plant kingdom. AHL1 localizes preferentially in the boundary region between euchromatin and heterochromatin. The other nuclear protein encodes an Aurora kinase (AtAUR). AtAUR 1 and 2 localizes in mitotic spindles and AtAUR3 accumulates in kinetochore regions of mitotic chromosomes. The plant Aurora kinase regulates phosphorylation of Ser10 and Ser28 of histone H3. Lagging chromosomes and micronuclei were observed frequently in the Aurora kinase inhibitor Hesperadin-treated BY-2 cells, suggesting that the plant Aurora kinase may have a role in chromosome segregation and metaphase/anaphase transition.
