We have identified by cDNA cloning a gene, denoted MPS-1, that is activated in cultured human transformed cells by growth factors. The MPS-1 gene contains one zinc finger domain similar to those present in the C4 family of DNA binding proteins. In this study, the expression of MPS-1 mRNA and protein were examined in HPV-induced human condylomata acuminata. Initially, we detected the presence of MPS-1 mRNA by message amplification phenotyping in all condylomata tissues examined. Subsequently, the cellular distribution and abundance of MPS-1 mRNA was studied by in situ hybridization with specific MPS-1 DNA and RNA probes. We found that MPS-1 mRNA is expressed at high levels in the cytoplasm of condylomata cells. In contrast, the MPS-1 mRNA is expressed at low levels in nonneoplastic tissues. Moreover, antibodies were raised against the predicted N-terminal sequence of the MPS-1 protein and used to detect MPS-1 in condylomata cells. MPS-1 immunoreactivity was detected in the cytoplasm and/or the perinuclear regions of condylomata cells, with marked staining in areas of active proliferation. In distinction, MPS-1 immunoreactivity was very weak in normal epithelial cells. The results support the contention that the MPS-1 protein may be a potentially important mediator of proliferative responses induced by HPV.