Identification and characterization of a novel upstream promoter of zebrafish p53 gene.

Background: It is widely acknowledged that the p53 gene can be expressed as multiple isoforms with different functions, however the transcriptional mechanism of p53 still needs further investigation. Here we identified an elevated transcription signal about 3.6 kb upstream of the p53 promoter in cold acclimated zebrafish ZF4 cells.

Methods and results: Through rapid amplification of cDNA ends (RACE), an unreported p53 transcript was cloned, which is transcribed from a novel upstream promoter about 3.6 kb from the canonical p53 promoter. This Novel p53 transcript includes a novel 5'untranslated region (5'UTR) transcribed from the - 3.6 kb region, which is followed by the coding sequences (CDS) encoding wild type (WT) p53 protein. This Novel p53 transcript showed remarkably enhanced stability than WT p53 and Δ113p53 mRNAs, when its novel 5'UTR showed the lowest translation efficiency in luciferase assay. Novel p53 transcript is differentially expressed in various tissues and during different stages of embryonic development of zebrafish. Novel p53 transcript also showed different responses to different stimuli.

Conclusions: A novel upstream promoter about 3.6 kb from the canonical P1 promoter of zebrafish p53 gene was found, which transcribes a novel p53 transcript that contains a new 5'UTR and the CDS encoding WT p53 protein. The findings of our study will enhance the current knowledge on the regulation and functionality of the p53 gene in fish.