Induction of prothrombinase fgl2 by the nucleocapsid protein of virulent mouse hepatitis virus is dependent on host hepatic nuclear factor-4 alpha.
Fibrinogen-like protein 2/fibroleukin (Fgl2) plays a pivotal role in the pathogenesis of both experimental and human fulminant hepatic failure. We have reported recently that the nucleocapsid (N) protein from strains of murine hepatitis virus (MHV-3, MHV-A59), which cause massive hepatocellular necrosis but not from strains (MHV-JHM, MHV-2) which do not produce serious liver disease, induces transcription of fgl2. The purpose of the present study was to characterize both viral and host factor(s) necessary for viral induced transcription of fgl2. Mutation of residues Gly-12, Pro-38, Asn-40, Gln-41, and Asn-42 within domain 1 of the N protein of MHV-A59 to their corresponding residues found in MHV-2 abrogated fgl2 transcription, whereas mutation of other N protein domains, including a protein expressed from an internal reading frame (I protein), did not affect fgl2 gene transcription. We then examined the -372 to -306 sequence within the 1.3-kb fgl2 promoter region upstream from the transcription start site that was previously identified as necessary for N protein-induced gene transcription. We demonstrated that the -331/-325 HNF4 cis-element and its cognate transcription factor, HNF4alpha, are necessary for virus-induced fgl2 gene transcription. In uninfected macrophages and macrophages infected with MHV-2, an unidentified protein occupies the HNF4 cis-element. Following stimulation with MHV-A59, it was shown by electrophoretic mobility shift assay that HNF4alpha binds the HNF4 cis-element in the fgl2 promoter. We further report the unprecedented presence of HNF4alpha in peritoneal macrophages. Collectively, the results of this study define both viral and host factors necessary for induction of fgl2 prothrombinase gene transcription in MHV infection and may provide an explanation for the hepatotrophic nature of MHV-induced fulminant hepatic failure.
Ning
Qin
Q
Department of Infectious Disease, Institute of Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China. qning@tjh.tjmu.edu.cn
Lakatoo
Sophia
S
Liu
Mingfeng
M
Yang
Weiming
W
Wang
Zhimo
Z
Phillips
M James
MJ
Levy
Gary A
GA
D000595:Amino Acid Sequence; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D016466:CHO Cells; D006224:Cricetinae; D004268:DNA-Binding Proteins; D005260:Female; D005340:Fibrinogen; D005786:Gene Expression Regulation; D006509:Hepatitis B / Q000209:etiology; D006526:Hepatitis C / Q000209:etiology; D051557:Hepatocyte Nuclear Factor 4; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D006517:Murine hepatitis virus / Q000472:pathogenicity*; D019590:Nucleocapsid Proteins / Q000737:chemistry / Q000502:physiology*; D010750:Phosphoproteins / Q000502:physiology*; D011401:Promoter Regions, Genetic; D013925:Thromboplastin / Q000096:biosynthesis* / Q000235:genetics; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C490637:Fgl2 protein, mouse; D051557:Hepatocyte Nuclear Factor 4; C496593:Hnf4a protein, mouse; D019590:Nucleocapsid Proteins; D010750:Phosphoproteins; C501970:Tcfl4 protein, mouse; D014157:Transcription Factors; D005340:Fibrinogen; D013925:Thromboplastin