Molecular Characterization of Paralichthys olivaceus MAF1 and Its Potential Role as an Anti-Viral Hemorrhagic Septicaemia Virus Factor in Hirame Natural Embryo Cells

Abstract

MAF1 is a global suppressor of RNA polymerase III-dependent transcription, and is conserved from yeast to human. Growing evidence supports the involvement of MAF1 in the immune response of mammals, but its biological functions in fish are unknown. We isolated and characterized <i>Maf1</i> from the olive flounder <i>Paralichthys olivaceus</i> (<i>PoMaf1</i>). The coding region of <i>PoMaf1</i> comprised 738 bp encoding a 245-amino-acid protein. The deduced PoMAF1 amino acid sequence shared features with those of MAF1 orthologues from vertebrates. <i>PoMaf1</i> mRNA was detected in all tissues examined, and the levels were highest in eye and muscle tissue. The <i>PoMaf1</i> mRNA level increased during early development. In addition, the <i>PoMaf1</i> transcript level decreased during viral hemorrhagic septicemia virus (VHSV) infection of flounder hirame natural embryo (HINAE) cells. To investigate the role of <i>PoMaf1</i> in VHSV infection, single-cell-derived <i>PoMaf1</i> knockout HINAE cells were generated using the clustered regularly interspaced short palindromic repeats/CRISPR-associated-9 (CRISPR/Cas9) system, and cell clones with complete disruption of <i>PoMaf1</i> were selected. <i>PoMaf1</i> disruption increased the VHSV glycoprotein (G) mRNA levels during VHSV infection of HINAE cells, implicating PoMAF1 in the immune response to VSHV infection. To our knowledge, this is the first study to characterize fish <i>Maf1</i>, which may play a role in the response to viral infection.