A CDC5(-PLANT, ARABIDOPSIS-THALIANA() HOMOLOG OF A HIGHER)

We cloned and characterized a cDNA corresponding to a cdc5(+) homolog of the higher plant, Arabidopsis thaliana. The cDNA, named AtCDC5 cDNA , encodes a polypeptide of 844 amino acid residues. The amino acid seq uence of N-terminal one-fourth region of the predicted protein bears s ignificant similarity to that of Schizosaccharomyces pombe Cdc5 and My b-related proteins. Overexpression of the AtCDC5 cDNA in S. pombe cell s is able to complement the growth defective phenotype of a cdc5 tempe rature-sensitive mutant. These results indicate that the AtCDC5 gene i s a plant counterpart of S. pombe cdc5(+). This is the first report of a cdc5(+)-like gene in a multicellular organism. We also demonstrated that a recombinant AtCDC5 protein possesses a sequence specific DNA b inding activity (CTCAGCG) and the AtCDC5 gene is expressed extensively in shoot and root meristems. In addition, we cloned a PCR fragment co rresponding to the DNA binding domain of human Cdc5-like protein. Thes e results strongly suggest that Cdc5-like protein exists in all eukary otes and may function in cell cycle regulation.