Profiles of teleost DNA fragmentation factor alpha and beta from rock bream (Oplegnathus fasciatus): molecular characterization and genomic structure and gene expression in immune stress

Abstract

Apoptosis serves to protect normal cells during the processes of development, aging, tissue homeostasis, immunity, and inflammation. Molecules such as caspases, the Bcl-2 family proteins, cytochrome c, APAF-1, and apoptotic endonucleases are concerned with and regulate different stages of apoptosis. DNA fragmentation factor (DFF) is a key final molecule in chromosomal DNA fragmentation during the last step of apoptosis, and is a heterodimeric complex consisting of alpha/inhibitor of caspase-activated DNase (DFFA/ICAD) and beta/caspase-activated DNase (DFFB/CAD) subunits. DFFB/CAD is normally combined with the inhibitor, DFFA/ICAD, in healthy cells. However, after cleavage of the DFF complex by effector caspases, DFFB/CAD acts as an apoptotic nuclease and induces DNA fragmentation in apoptotic cells. The study of DFF proteins is focused on the roles of the apoptotic pathway in mammals. However, gene expression and functions under immune stimulation are not well known in other species. In the present study, we first characterized teleost DFFA/ICAD and DFFB/CAD from rock bream at the molecular level and analyzed the transcriptional expression pattern under immune challenges, to understand their role in immunity. These putative proteins have shown conserved domains and interaction sites orthologous to those of other species. High mRNA expression of both genes was found in the gills and blood of tissues involved in the immune response. The increased expression of DFF genes upon bacterial and viral stimulation was confirmed by qPCR analysis. DFFA/ICAD and DFFB/CAD of rock bream may play a pivotal role in apoptosis and may be involved in host immunity against bacterial and viral infection.