Expression of mRNA homologous to interleukin 1 in human epidermal cells

Epidermal cells produce an interleukin 1 (IL-1)-related molecule known as epidermal cell-derived thymocyte activating factor (ETAF). Given their similar physical and biologic properties, it was presumed that ETAF would share homology to known IL-1 sequences. A murine IL-1 alpha complimentary DNA (cDNA) probe hybridized with a 2.1 kb RNA from the murine keratinocyte cell line PAMM 212. Further, a 24-base synthetic IL-1 beta probe complementary to a region 700 bases from the putative 5'-end of human IL-1 beta hybridized with 2.7- and 1.6-kb RNAs in human keratinocytes, monocytes, and promyelocytic leukemia cells. Reverse transcripts primed with the IL-1 beta oligonucleotide revealed major first-strand cDNAs from human keratinocyte COLO-16 cell mRNA and human monocyte mRNA of about 700 bases, consistent with the expected cDNA from IL-1 beta. A partial library constructed from this cDNA contained clones that hybridized with the IL-1 beta oligonucleotide. The 750 bp-IL-1 beta-like cDNA clones were not identical to IL-1 beta as judged by restriction mapping and Northern analysis. These cDNA clones hybridized with the 1.6-kb keratinocyte mRNA but not to the 1.6-kb monocyte nor to the 2.7-kb mRNA. The 1.6-kb keratinocyte mRNA may encode a new IL-1-like species.