CHARACTERIZATION OF HUMAN N8 PROTEIN

We have shown before that the N8 mRNA is expressed at higher levels in lung tumor and lung tumor-derived cell lines than normal lung cells. In this paper, we have characterized the N8 protein, and studied its p roperties. The N8 gene encodes a major 24 kDa protein and its expressi on correlates well with the N8 mRNA expression pattern observed in dif ferent cell lines. N8 protein is capable of forming a homodimer or mul timeter in vitro. It is a phosphorylated cytoplasmic protein and phosp horylation occurs mainly at serine residues, N8 protein is expressed a t higher levels in epithelial cells than in mesenchymal cells, Ns prot ein expression is induced in a fibroblast cell line expressing adenovi ral Ela protein, which acquired epithelial-like characteristics. Furth ermore, ectopic expression of N8 protein in NIH3T3 cells converts them into a spheroid form. These spheroids also have some of the character istic features of epithelial cells. Taken together, these results sugg est that the N8 protein may be associated with the development or main tenance of epithelial cell phenotype.