Isolation, sequencing and bioinformatics analysis of regulatory elements in C3 gene promoter region of Salmon fish(Salmo salar)

The complement system is one of the main components of the immune system in many organisms. The existence of this system has been confirmed in numerous organisms, but there is no information about the mechanisms regulating the expression of it in some of them. In this study, we have focused on the upstream element of salmon fish C3 gene. Different tissues of the fish were prepared and DNA was extracted with a modified phenol-chloroform method. Target sequence was amplified using unclassical PCR method by using of designed degenerate primers and PCR product was purified and sequenced and finally confirmed sequence was recorded in Genomic Bank Database. In the next step, a full anatomy of obtained sequence was examined for the presence of regulatory elements by application of different servers and software. Salmon fish C3 gene promoter region sequence was recorded in NCBI genomic data bank with accession number JQ799884.1. The presence of conserved TATA box and abaA, C/EBP, CTCF, IL-6, GR and PPAR transcription factors responsive elements were confirmed, however, responsive element sequence for factors such as Sp1, CRE, ERE were not detected. Our results can confirm the existence of an evolutionary well-developed regulatory system on the complement system in bony fishes and support ancestral nature of complement system genes. This study is the first detailed report on the regulatory elements controlling gene expression of the C3 gene and may suggest the involvement of complement derivatives in the early embryonic development steps that have been reported in some study.