Molecular characterization of the first non-mammalian p73 cDNA

The p53 gene is believed to be mutated or deficient in over 50% of human tu mours, and is therefore considered to be instrumental in the process of car cinogenesis. Recently in humans, homologues of p53 (such as p73 and p63) ha ve been isolated. In our studies in fish, we have been isolating tumour sup pressor genes with a view to their potential use to study genotoxins in the aquatic environment. In this paper, we report the characterisation of the first non-mammalian p73 cDNA, isolated from barbel (Barbus barbus), a fresh water cyprinid fish indigenous to UK rivers. The deduced barbel p73 amino a cid sequence has a high homology with human p73 alpha: the proteins are 641 and 636 aa in length, respectively, and there is a 72% identity over the e ntire sequence length of the protein (over 90% in the putative DNA binding domain). The level of conservancy for p73 is considerably higher across cla ss (from man to fish), than for p53 and it may therefore have particular va lue in studies on environmental mutagenesis. Northern analysis showed expre ssion of three p73 mRNA transcripts/homologues. The patterns of p73 tissue expression in the barbel differed from the expression of p53 mRNA, suggesti ng specific functional roles for thr two genes. (C) 2000 Elsevier Science I nc. All rights reserved.