Specific expression and regulation of the new melanoma inhibitory activity-related gene MIA2 in hepatocytes

The novel human gene MIA2 encoding a melanoma inhibitory activity (MIA) homologous protein was identified by a GenBank(TM) search. MIA2, together with MIA, OTOR, and TANGO, belongs to the novel MIA gene family sharing important structural features, significant homology at both the nucleotide and protein levels, and similar genomic organization. In situ hybridization, reverse transcriptase-PCR, and Northern blots presented a highly tissue-specific MIA2 expression pattern in the liver. Promoter studies analyzing transcriptional regulation of MIA2 revealed an HNF-1-binding site at position -236 controlling hepatocyte-specific expression. Mutation of the site led to a complete loss of promoter activity in HepG2 cell. Further sites detected in the MIA,2 promoter were consensus binding sites for SMAD and STAT3, Consistently, stimulation of MIA2 mRNA expression occurred by treatment with interleukin-6, transforming growth factor-beta, and conditioned medium from activated hepatic stellate cells. In accordance with these results, MIA2 mRNA was found to be increased in liver tissue of patients with chronic hepatitis C infection compared with controls. MIA2 mRNA levels were significantly higher in patients with severe fibrosis or inflammation than in patients with less severe fibrosis or inflammation. In summary our data indicate that MIA2 represents a potential novel acute phase protein and MIA2 expression responds to liver damage. The increased transcription in more severe chronic liver disease suggests that MIA2 may serve as a marker of hepatic disease activity and severity.