Keratin gene expression in simian virus 40-transformed human keratinocytes

Previous reports from this laboratory indicate that cultured simian virus 40 (SV40)-transformed human keratinocytes express keratin proteins characteristic of simple epithelia that are not found in their untransformed counterparts. In this study we show by in vitro translation and RNA transfer blot analysis that the altered keratin synthesis reflects changes in the abundance of specific keratin mRNAs. SV40-transformed keratinocytes have a reduced abundance of transcripts for 58-, 56-, 52-, 50-, 48-, and 46-kDa keratin species, compared with uninfected cultured keratinocytes, but express significant levels of transcripts for 52-, 45-, and 40-kDa keratins, typical of simple epithelia. The SV40-transformed cells also express mRNA for a 48-kDa keratin that is unique to SV40-transformed keratinocytes. Analysis of the keratin genome with keratin-specific cDNAs as probes indicates that the changes in keratin transcription are not correlated with gross rearrangements of the keratin genome. These results suggest that analysis of viral transformation of cultured keratinocytes affords a novel approach to study mechanisms regulating keratin gene expression.