The MUC1 gene encodes a mucin glycoprotein and is overexpressed in breast cancer. Knowledge of the mechanisms leading to MUC1 overexpression may help in the development of molecular approaches for breast cancer therapy. In order to study the regulation of the MUC1 gene transcription, we analyzed functional activities of various deletion mutants of the MUC1 promoter. We established that transcriptional cis-elements present in the SacI/XmnI fragment of the promoter are competent and sufficient for expression of, at least, tandem repeats containing isoform(s) of the MUC1 protein. CAT transfection analysis showed that both the 3' and 5' regions of the SacI/XmnI fragment possess transcription activities. Promoter activities associated with the SacI/XmnI fragment were confirmed by a RNase protection assay, which demonstrated multiple transcription start sites (TSSs) in the MUC1 gene transcribed in epithelial T47D cells. We show that treatment of the T47D cells with TGFβ1 leads to activation of additional TSSs in the MUC1 gene. The roles of the structural and functional properties of the MUC1 promoter in MUC1 gene transcription are discussed. Copyright (C) 1999 Federation of European Biochemical Societies.
Bibliographical noteFunding Information:
We thank Dr M. Hareuveni for providing us with the pHMG/CL642/MUC1 plasmid, Dr I. Tsarfaty for pUN121 plasmid containing the MUC1 gene sequence, Prof. A. Yaniv and Prof. A. Gazit in whose laboratory the CAT assays were performed and Dr M. Gorivodsy for help in computer analysis. This research was supported by the Israel Cancer Association, the Simco Chair for Breast Cancer Research, the Federico Fund for Tel Aviv University and the Barbara Friedman Fund (I.K.) and Susan Komen Breast Cancer Foundation (D.H.W.).
- CAT assay
- MUC1 gene
- Transcription start site