The human cell cycle gene CDC25B is located at 20p13.

Abstract

Central to the onset of mitosis in all eucaryotic cells is the CDC2 protein kinase, the activity of which is negatively regulated by phosphorylation, and positively activated by dephosphorylation (5). The latter function is carried out by a novel phosphatase, cdc25 (4). There appear to be at least three human CDC25 genes that code for A (3), B (3), and C (6) forms of cdc25. The gene for cdc25C was recently mapped to chromosome band 5q31 by fluorescence in situ hybridization (FISH) (7); however, genes for cdc25A and cdc25B have not yet been chromosomally assigned. A cDNA clone (CentroV), isolated from a [lambda]gt11 expression library constructed from the human melanoma cell line A2058 (Clontech), contained a 2.6-kb insert upon partial digestion with EcoRI and fragments of 1.2 and 1.4-kb upon complete digestion. Sequencing of the cDNA clone showed it to be derived from part of the CDC25B mRNA corresponding to nucleotides 307 to 2898 of the previously sequence (3). The 1.2- and 1.4-kb fragments were nick-translated with biotin-14-dATP and hybridized in situ simultaneously at a final concentration of 5 ng/[mu]l to metaphases from two normal males. The FISH method was modified from that previously described (1) in that chromosomes weremore » stained before analysis with both propidium iodide (as counterstain) and DAPI (for chromosome identification). Twenty metaphases from the first normal male were examined for fluorescent signal. Nineteen of these metaphases showed signal on one or both chromatids of chromosome 20 in the region 20p12-p13; 93% of this signal was at 20p13. There was a total of 17 nonspecific background dots observed in these 20 metaphases. A similar result was obtained from the hybridization to the second normal male.« less