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 Maf1 from the olive flounder Paralichthys olivaceus (PoMaf1). The coding region of PoMaf1 comprised 738 bp encoding a 245-amino-acid protein. The deduced PoMAF1 amino acid sequence shared features with those of MAF1 orthologues from vertebrates. PoMaf1 mRNA was detected in all tissues examined, and the levels were highest in eye and muscle tissue. The PoMaf1 mRNA level increased during early development. In addition, the PoMaf1 transcript level decreased during viral hemorrhagic septicemia virus (VHSV) infection of flounder hirame natural embryo (HINAE) cells. To investigate the role of PoMaf1 in VHSV infection, single-cell-derived PoMaf1 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 PoMaf1 were selected. PoMaf1 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 Maf1, which may play a role in the response to viral infection.
Highlights
MAF1, a central RNA polymerase III-associated transcription repressor, is highly conserved from yeast to human [1]
The P. olivaceus Maf1 (PoMaf1) mRNA level was highest in eye tissue in P. olivaceus and markedly increased during early development
MRNA level in hirame natural embryo (HINAE) cells decreased during viral hemorrhagic septicemia virus (VHSV) infection
Summary
MAF1, a central RNA polymerase (pol) III-associated transcription repressor, is highly conserved from yeast to human [1]. MAF1 was discovered in the yeast, Saccharomyces cerevisiae [2]. MAF1 represses RNA pol III in response to unfavorable growth conditions, such as oxidative stress, DNA damage, rapamycin or chlorpromazine treatment, and secretory pathway inhibition [3]. MAF1 represses RNA pol IIIdependent transcription, and RNA pol II-dependent transcription of the transcription initiation factor, TATA-binding protein (TBP) [4]. Because TBP is required for the function of RNA pol I, MAF1 can impact transcriptional activity directly and indirectly [5]. Phosphorylated MAF1 is localized at the promoters of tRNA and 5S rRNA genes, and represses their expression [6]
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