cDNA cloning and expression analysis of flounder p53 tumour suppressor gene

The screening of a flounder cDNA library with a rainbow trout p53 probe allowed the isolation of a 2.8-kb fragment homologous to human (50%) and rainbow trout (57%) p53 coding sequences. The fragment contains a single open reading frame coding for a 366-amino acid protein. The predicted amino acid sequence is relatively divergent from other p53 proteins but it displays the main p53 features: five highly conserved domains, an acidic N-terminus, a hydrophilic and charged C-terminus, a penultimate serine residue and a putative nuclear localization signal. Furthermore, conservation of critical amino acids and comparable distribution of charge and hydrophobicity suggest that flounder p53 properties could be similar to those in mammals. Northern blot analysis revealed a single transcript of about 3 kb in the flounder ovary tissues. In fact, RT-PCR showed an ubiquitous but very low expression of p53 gene in all flounder tissues.