Cloning, characterization and expression analysis of the gene for a putative lipopolysaccharide-induced TNF-alpha factor of the Pacific oyster, Crassostrea gigas.

Lipopolysaccharide-induced TNF-alpha factor (LITAF) is an important transcription factor that mediates the expression of inflammatory cytokines, including TNF-alpha, in lipopolysaccharide (LPS)-induced processes. In the present study, the Pacific oyster Crassostrea gigas LITAF (Cg-LITAF) gene was cloned and characterized. The full-length Cg-LITAF cDNA consists of 906bp and encodes a polypeptide of 115 amino acids. The Cg-LITAF gene consists of three exons and two introns, with a length of approximately 1.8kb. The Cg-LITAF protein showed 34-45% amino acid sequence identity with other known LITAF sequences. Although the Cg-LITAF coding sequence (115 aa) is shorter than all previously reported LITAF genes, the LITAF domain which contains two CXXC motifs is well conserved. An in vivo expression study showed that Cg-LITAF mRNA was expressed predominantly in gills and moderately in digestive gland and labial palps of healthy oysters. The accumulation of Cg-LITAF mRNA in oyster haemocytes determined by real-time PCR showed the peak 12h after bacterial challenge. This expression pattern suggests that Cg-LITAF is a potent factor in the regulation of genes that are involved in innate defence mechanisms.