Basal regulatory promoter elements of the hsp27 gene in human breast cancer cells.

The small human heat shock protein hsp27 has been shown to play important roles in diverse cellular processes such as actin polymerization, thermotolerance, growth, and chemotherapeutic drug resistance. Two breast cancer cell lines MCF-7 and MDA-MB-231 were used as a model to study the molecular mechanisms important for basal hsp27 promoter transcriptional activity. A genomic clone containing 1.1 kb of the hsp27 promoter was sequenced and the regulatory elements were characterized. The first 200 bp within this 5'-flanking region holds the majority of the transcriptional activity, according to transient transfection assays using a series of hsp27 promoter deletion fragments in luciferase reporter vectors. The basal activity of this fragment is largely confined to a G/C-rich region containing overlapping SP1 and AP2 transcription factor binding sites.