We have investigated the control of vimentin expression in human breast cancer cell lines because of its transcriptional activation during malignant progression in breast cancer. Comparison of vimentin-positive (V+) and vimentin-negative (V-) breast cancer cell lines revealed several potential areas of vimentin gene regulation. Analysis of the chromatin structure of the vimentin gene in V+ and V- breast cancer cells showed DNase I hypersensitive sites in the 5' promoter region in V+ cell lines and 3' to the start of transcription in V- cell lines. Promoter deletion and reporter gene analysis revealed the importance of two adjacent AP-1 sites separated by seven GC- rich nucleotides for vimentin expression in V+ breast cancer cells. Mutational analysis of these sequences showed that although both AP-1 sites could bind nuclear proteins from V+ cells in vitro, one AP-1 site was sufficient to drive transcription in CAT reporter gene assays. The GC-rich spacer region had a modulating function on the activity of the AP-1 sites. In addition, levels of c-jun mRNA were elevated in V+ versus V- cells. In summary, distinct sites within the vimentin gene appear to be important for the control of vimentin expression in V+ and V- breast cancer cells with multiple elements acting coordinately to regulate vimentin expression.
|Number of pages
|Cell Growth and Differentiation
|Published - 1994