Molecular cloning and sequencing of cDNAs encoding homologues of human Ku70 and Ku80 autoantigen from Xenopus and their expression in various Xenopustissues

We isolated cDNA clones encoding Ku70 and Ku80 homologues of Xenopus laevis from a cDNA library prepared from Xenopus oocytes. The nucleotide sequence s of these Ku70 and Ku80 homologues have coding sequences of 1833 bp and a 611 aa protein, and 2178 bp and a 726 aa protein, respectively. The amino a cid sequences deduced from the open reading frame of the Ku70 and Ku80 cDNA clones were highly homologous to those from Ku genes previously isolated, such as human (ca. 65% and ca. 62% identity, respectively) and mouse (ca. 6 5% and ca. 60%), and show a certain degree of homology to Drosophila (ca. 2 7% with Ku70), Caenorhabditis elegans (ca. 20% with Ku80) and Saccharomyces cerevisiae (ca. 23% and ca. 19%). Our detailed comparison of the predicted amino acid sequences among these species revealed the highly conserved oct a-peptide LPFXXDIR common to both Xenopus Ku70 and Ku80 homologues in the r egion showing the high homology throughout the species tested. A Northern a nalysis using specific cDNA probes showed that Ku poly(A)(+) mRNAs are expr essed at high levels in Xenopus adult oocyte and testis. (C) 1999 Elsevier Science B.V. All rights reserved.