Molecular cloning, characterization and expression analysis of p53 from turbot Scophthalmus maximus and its response to thermal stress

Molecular cloning, characterization and expression analysis of P53 from high latitude fish Phoxinus lagowskii and its response to hypoxia

As an intermediate link between multiple cellular stresses and cellular responses, p53, together with its upstream and downstream regulators and related genes, constitutes a complex network that regulates cellular stresses and cellular responses. However, no studies have investigated p53 in Phoxinus lagowskii, particularly the expression of p53 under different hypoxic conditions. In the present study, the cDNA of p53 from the Phoxinus lagowskii was cloned by the combination of homology cloning and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of Pl-p53 was 1878 bp, including an open reading frame (ORF) of 1116 bp encoding a polypeptide of 371 amino acids with a predicted molecular weight of 41.22 kDa and a theoretical isoelectric point of 7.38. Quantitative real-time (qRT) PCR assays revealed that Pl-p53 was commonly expressed in all tissues examined, with highest expression in the heart. In addition, we investigated the expression of Pl-p53 in different tissues under different hypoxic conditions. In the short-term hypoxia group, Pl-p53 expression was down-regulated in both the brain and heart. The Pl-p53 expression was significantly elevated at 6 h in the muscle and liver, and was significantly up-regulated at 24 h in spleen. These results suggest that Pl-p53 plays different regulatory roles and provide a theoretical basis for the changes of p53 in fish facing hypoxic environments.

Molecular characterization of ubiquitin-conjugating enzyme gene ube2h and siRNA-mediated regulation on targeting p53 in turbot, Scophthalmus maximus

Ubiquitin-conjugating enzymes are key factors in the ubiquitin proteasome pathway (UPP), which play key roles in ubiquitination. These enzymes affect the efficiency of UPP during stress conditions. P53 has important control of cell cycle arrest and apoptosis in response to cellular stress; these modifications are critical for the stability and transcriptional activity of p53 as the protein activates downstream target genes that dictate the cellular response. However, few studies have investigated the effects of thermal stress in turbot (Scophthalmus maximus), specifically the UPP signaling pathway, and the crosstalk between the ube2h and p53. In this study, the rapid amplification of cDNA ends was used to obtain a full-length cDNA of the turbot UBE2H gene (Sm-ube2h) and perform bioinformatics analysis. Our results showed that the cDNA of the Sm-ube2h was 718 bp in length, encoding a 189 amino acid protein, with a theoretical isoelectric point of 4.77. It also contained a catalytic (UBCc) domain. Expression of Sm-ube2h in different tissues was detected and quantified by qPCR, which was highest in the spleen and lowest in the liver. We also investigated the Sm-ube2h expression profiles in the liver and heart after thermal stress, and changes in Sm-ube2h and p53 under thermal stress, upon RNA interference. Our data speculated that Sm-ube2h and p53 exhibited antagonistic effects under normal temperature conditions after ube2h interference, but displayed synergistic effects under thermal stress, suggesting the crosstalk between UPP and p53 signaling pathway. Our results improved our understanding of the underlying molecular mechanism of thermal tolerance in turbot.

Heat stress-induced HSP90 expression is dependent on ERK and HSF1 activation in turbot (Scophthalmus maximus) kidney cells

Mitogen-activated protein kinases (MAPKs) and heat shock proteins (HSPs) are ubiquitous proteins that are functional mediators in both normal and stressed states of the cell. In this study, we performed heat stress (37 °C) experiments on turbot kidney (TK) cells. Heat stress expression patterns of HSP90, as well as the expression and phosphorylation levels of extracellular-regulated signal kinases (ERKs) and the transcription factor HSF1 and c-Fos, were examined. The results show that heat stress activates ERK1/2 and HSF1, and induces HSP90 gene expression in TK cells. Inhibition of ERK activation attenuates heat stress-induced HSP90 gene expression. The double luciferase reporter gene experiment showed that HSF1 is an important transcription factor for heat-induced HSP90 gene expression. Likewise, c-Fos does not directly regulate the heat-induced expression of HSP90 in turbot kidney cells. To our knowledge, this is the first study to report a signaling pathway that regulates the heat shock response in turbot cells. Our results may facilitate an understanding of the underlying molecular mechanisms of the cellular stress response in marine fish.