Identification of a 42-kDa nuclear factor (NF1-MUC5B) from HT-29 MTX cells that binds to the 3' region of human mucin gene MUC5B.

MUC5B gene is one of the four human mucin genes mapped to chromosome 11p15. The identification of three potential Sp1 binding sites located between the tandem repeat and the 3' end of MUC5B suggests a possible regulatory role for this region. In this report we show by electrophoretic mobility shift assay that only one potential Sp1 binding site (NAU62) leads to a specific interaction with a nuclear factor from HT-29 MTX cells which does not exist in parental HT-29 cells. By using mutated versions of NAU62, an 18 mer sequence within this later was shown to be directly involved in the interaction. The nuclear factor called NF1-MUC5B which binds to this element has a Mr of 42000 and is not Sp1. These results suggest that MUC5B contains a sequence in its 3' region that might act as a cis-element. This report opens the field of transcriptional regulation of human mucin genes encoding secreted mucins.