Identification, sequence analysis and characterization of Clonorchis sinensis ubiquitin.

Ubiquitin is a functionally important protein expressed in eukaryotic cells usually encoded by multigenic families containing two types of genes, ubiquitin extension genes and polyubiquitin genes. One independent monomeric locus and two independent polyubiquitin loci were firstly identified from the genome of carcinogenic liver fluke, Clonorchis sinensis (C. sinensis). The nucleotide and amino acid sequence of C. sinensis polyubiquitin, especially polyubiquitin with five tandem ubiquitin repeats (CsPUB5), were analyzed. We obtained recombinant CsPUB5 (rCsPUB5) and anti-rCsPUB5 IgG. The ubiquitin transcripts in life cycle of C. sinensis were investigated. In addition, we found that ubiquitin or ubiquitination was ubiquitous in adult worm of C. sinensis and significantly observed in the content of biliary tract and intrahepatic biliary epithelium of liver from C. sinensis infected rat. We confirmed that rCsPUB5 could bind to human intrahepatic biliary epithelial cell by immunofluorescence in vitro. It was considered that ubiquitin family constitutively expressed in C. sinensis for variety of cellular processes and might be implicated in the genesis and progression of cholangiocarcinoma induced by the infection of C. sinensis.