EXPRESSION OF THE PUTATIVE PROTOONCOGENE HIS-1 IN NORMAL AND NEOPLASTIC TISSUES

The His-1 gene is expressed as a 3-kb spliced and polyadenylated RNA t hat is believed to function in the absence of an encoded protein. The precise function of the His-1 gene is unknown, but its transcriptional activation in a series of mouse leukemias has implicated the His-1 RN A in leukemogenesis when it is abnormally expressed To study the oncog enic potential of this gene in more detail, we have examined the norma l tissue distribution of His-1 RNA during mouse embryogenesis and in v arious adult tissues, His-1 expression was detected at low levels in t he epithelia of the adult mouse stomach, prostate, seminal vesicle, an d the developing choroid plexus by in situ hybridization. All other ti ssues examined lacked detectable levels of hybridizing RNA, suggesting that normal His-1 gene expression is highly restricted to these epith elial sites. These transcripts were not detectable by Northern blot an alysis of normal tissues but were readily identified in five mouse leu kemias and in five carcinomas of the choroid plexus. These data indica te that the His-1 gene expression is highly restricted and suggest tha t inappropriate activation of this gene may contribute to carcinogenes is.