Molecular cloning and sequence analysis of heat shock proteins 70 (HSP70) and 90 (HSP90) and their expression analysis when exposed to benzo(a)pyrene in the clam Ruditapes philippinarum.

Abstract HSP70 and HSP90 are the most important heat shock proteins (HSPs), which play the key roles in the cell as molecular chaperones and may involve in metabolic detoxification. The present research has obtained full-length cDNAs of genes HSP70 and HSP90 from the clam Ruditapes philippinarum and studied the transcriptional responses of the two genes when exposed to benzo(a)pyrene (BaP). The full-length Rp HSP70 cDNA was 2336 bp containing a 5′ untranslated region (UTR) of 51 bp, a 3′ UTR of 335 bp and an open reading frame (ORF) of 1950 bp encoding 650 amino acid residues. The full-length Rp HSP90 cDNA was 2839 bp containing a 107-bp 5′ UTR, a 554-bp 3′ UTR and a 2178-bp ORF encoding 726 amino acid residues. The deduced amino acid sequences of Rp HSP70 and Rp HSP90 shared the highest identity with the sequences of Paphia undulata , and the phylogenetic trees showed that the evolutions of Rp HSP70 and Rp HSP90 were almost in accord with the evolution of species. The Rp HSP70 and Rp HSP90 mRNA expressions were detected in all tested tissues in the adult clams (digestive gland, gill, adductor muscle and mantle) and the highest mRNA expression level was observed in the digestive gland compared to other tissues. Quantitative real-time RT-PCR analysis revealed that mRNA expression levels of the clam Rp HSP70, Rp HSP90 and other xenobiotic metabolizing enzymes (XMEs) (AhR, DD, GST, GPx) in the digestive gland of R. philippinarum were induced by benzo(a)pyrene (BaP) and the absolute expression levels of these genes showed a temporal and dose-dependent response. The results suggested that Rp HSP70 and Rp HSP90 were involved in the metabolic detoxification of BaP in the clam R. philippinarum .