Cloning and analysis of expression of Mx cDNA in Japanese flounder, Paralichthys olivaceus

Myxovirus resistance (Mx) is an interferon (IFN)-induced protein that speci fically prevents growth, in vivo and in vitro of certain classes of virus. We isolated the Mx cDNA from a leukocyte cDNA library obtained from a Japan ese flounder infected with Hirame rhabdovirus (HRV). The Mx cDNA was found to contain 2385 bp coding for 620 amino acids. The amino acid sequence had approximately 51 and 78% identities to the sequences of human and rainbow t rout Mx cDNAs, respectively. We propose that the amino acid sequence encode d by this cDNA clone contains a tripartite guanosine-5'-triphosphate (GTP)- binding motif, GXXXSGKS/T, DXXG and T/NKXD, and a signature of the dynamin family, LPRG(S/K)GIVTR, which are conserved in all IFN-induced Mx proteins of vertebrates. In addition, the C-terminal region of the Japanese flounder Mx protein, like those of other Mx proteins, contains a highly conserved l eucine zipper motif. Japanese flounder infected with the HRV showed increas ed expression of Mx mRNA in the leukocytes starting at 48 h and peaking at 72 h. An RT-PCR (reverse transcription-polymerase chain-reaction) analysis of Mx mRNA from a healthy fish showed that the Mx mRNA was predominantly ex pressed in the kidney, spleen, intestine, brain, peritoneal cavity fluid an d gill, and only minimally expressed in leukocytes, liver, muscle and mucus . (C) 2000 Elsevier Science Ltd. All rights reserved.