RESUMO
Three methods were used in succession to screen a whole adult zebrafish cDNA library for expressed p53-like genes. The sequences of the resultant clones describe an open reading frame 1122 nucleotides in length, with another 43 and 940 bases of 5' and 3' untranslated sequence, respectively. The deduced amino acid sequence of the zebrafish p53 protein is 63% identical to that of trout and 48% identical to that of human p53. Two of the three zebrafish clones overlap to span the entire reported cDNA sequence and are identical in their deduced amino acid sequence over their coincident length. The third clone contains a conservative amino acid change, as well as an inserted amino acid subsequently found to be at the junction of exons 2 and 3, suggestive of alternative splicing in the p53 mRNA for this species. Northern analysis demonstrated a zebrafish p53-related transcript to be present and most abundant in zygotes and early-cleavage embryos less than 1 hour after fertilization, thereafter declining to barely detectable levels at 48 hours. A similar temporal expression was detected for the zebrafish L-myc, known to be present in maternally derived RNA, whereas zebrafish N-myc and the zebrafish homologue of the murine T gene were not detectable prior to the onset of zygotic transcription.
