Identification and functional characterization of the transcription factor coding Dp1 gene in large yellow croaker Pseudosciaena crocea

The transcription factor Dp1, as a binding partner, often forms a dimerization complex with typical E2F to play a central role in regulating gene expression during G1/S cell cycle progression. In this study, a full-length dp1 cDNA (Pcdp1) was successfully cloned and characterized from the large yellow croaker Pseudosciaena crocea. The nucleotidic sequence of Pcdp1 is 1,427 bp long with an open reading frame (ORF) of 1,239 bp encoding a putative protein of 412 amino acids, a 5'-untranslated region of 116 bp and a 3'-untranslated region of 70 bp. Prediction of protein domains showed that PcDp1 contains a DNA-binding domain (DBD) with a DEF box, a dimerization domain and an acidic region at C terminus with transcription activity. Homology comparisons indicated that PcDp1 shared the highest sequence identity of 98.55% with Oreochromis niloticus dp1, followed by 88.72% identity with Danio rerio dp1 and a relatively low identity of 78.91-80.55% with its mammalian and amphibian counterparts. The mRNA of Pcdp1 showed ubiquitously expression in all analyzed tissues, with the highest level of expression in the body kidney. Moderate expression levels of Pcdp1 was found in several immune-related tissues including the gills, head kidney and liver, indicating that PcDp1 might play an important role in osmotic pressure regulation and immune response of the large yellow croaker. The subcellular localization of PcDp1 revealed that it is mainly distributed in the cytoplasm both in COS-7 and parenchymal cells of the spleen, head kidney and kidney tissues. Furthermore, the recombinant PcDp1 exhibited DNA-binding activity to E2F site in vitro. In conclusion, these results indicated that PcDp1 may participate in immune regulation and provide a foundation for further study of the regulatory mechanism of Dp1 in teleosts.