RESUMEN
OBJECTIVE: To clone and identify the heat shock factors (HSFs) of Schistosoma japonicum and analyze its molecular structure and alternative splicing pattern. METHODS: The New Zealand rabbits were infected with the cercariae of Schistosoma japonicum and were killed and dissected 42 days post-infection, and the adult worms of S. japonicum and the livers of the rabbits were harvested. Then, the total RNA was extracted by using Trizol reagent. The Sj-hsf open reading frame (ORF) and the alternative splicing fragments were amplified by RT-PCR from the female, male and egg samples, then cloned and verified by enzyme digestion and sequencing. DNAMAN 8.0, InterPro, Mega 6 combined with the Internet databases were utilized to clarify the gene structure, functional domains, alternative splicing pattern, and the homology and phylogenetic tree of HSFs. RESULTS: Sj-hsf ORF and the alternative splicing fragments were amplified from the female, male and egg samples of S. japonicum by RT-PCR. After cloning, the positive recombinant plasmids pBSjHSFf-F, pBSjHSFf-M, pBSjHSFf-E containing Sj-hsf ORF, pBSjHSFs-F, pBSjHSFs-M, pBSjHSFs-E with Sj-hsf alternative splicing fragments were identified by enzyme digestion and sequencing. Three alternative splicing Sj-hsf isoforms were observed through sequence analysis: Sj-hsf-isoform1 (2 050 bp), Sj-hsf -isoform2 (2 086 bp) and Sj - hsf -isoform3 (2 111 bp); the GenBank accession numbers were KU954546, KX119143 and KX119144, respectively. All the three isoforms located in the same Contig SJC_S000780 of S. japonicum genome and all expressed at female, male and egg stages, but Sj-hsf-isoform1 with a high-level expression. Sj-HSF-isoform1 (671 aa) and Sj-HSF-isoform2 (683 aa) had DBD (DNA binding domain), HR-A/B and HR-C domains, while Sj-HSF-isoform3 (282 aa) stopped in advance without HR-C domain. Phylogenetic tree analysis of HSFs illustrated that Sj - HSFs belonged to HSF1 family, with a close phylogenetic relationship to Sm-HSFs. CONCLUSIONS: There are three alternative splicing isoforms of Sj-HSF existing in the female, male and egg stages of S. japonicum, but Sj-HSF-isoform1 expresses in a high-level. This study lays the foundation for further study on molecular mechanisms of Sj-HSFs in regulating the heat shock response system.