One of the isoforms of stem cell factor (SCF) was isolated from an embryonic kidney library with the ability to suppress the expression of cotransfected gene. The responsible region resides in the SCF 3' untranslated region (UTR). The SCF 5'UTR also has repressive element with a smaller effect than 3'UTR. The mRNA expression level of the cotransfected gene was not markedly changed. These results suggest that the SCF 3'UTR should negatively regulate gene expression at a posttranscriptional level. (C) 2003 Elsevier Inc. All rights reserved.