Abstract:Heat shock protein 90 (Hsp90) plays important roles in correct protein folding, intracellular material transport, cell proliferation regulation, and gametogenesis. In this study, the full-length cDNA of Hsp90 (SnHsp90) of Sipunculus nudus was cloned using RACE technology. The results showed that SnHsp90 is 3110 bp in length, including a 3´ UTR of 582 bp and a 5´ UTR of 72 bp. The open reading frame is 2456 bp in length and it encodes 818 amino acids. Sequence analysis showed that SnHsp90 has a signal peptide, with three tag sequences FLREL, IGQFGVGFYS, and LPLNVSRE and a conserved module, GxGxG, of type B Hsp90, thereby indicating that SnHsp90 belongs to the Hsp90B subgroup. Compared with other species, SnHsp90 showed the highest similarity (77.72%) with the Hsp90 of duck-billed bean sprouts. Three-dimensional structural modeling showed that the spatial conformation of Hsp90 among different species is highly conserved. Phylogenetic tree analysis showed that SnHsp90 was clustered into one branch of Hsp90 of annelids such as Capitella teleta and Helobdella robusta. The Hsp90 of all invertebrates was clustered into one branch, whereas that of the vertebrates was clustered into another branch, thus suggesting that SnHsp90 is closely related to the Hsp90 of Capitella teleta. RT-PCR results showed that SnHsp90 was expressed in different tissues of S. nudus, such as those of the body wall, muscles, and kidney tubes. SnHsp90 can also be expressed at different developmental stages of oocytes, and it is significantly expressed in Egg2 (oocyte in early stage of vigorous yolk synthesis) and Egg6 (excretive oocyte) (P<0.05). This result suggests the involvement of SnHsp90 in correct protein folding, yolk synthesis, and environmental stress resistance of S. nudus. The above results provide a basis for further exploration of the developmental mechanism of Sipunculus nudus oocytes.
