Cloning of an ets-Related Transcription Factor Involved in a Novel Epigenetic Mechanism of Mammary Carcinogenesis
Annual rept. 15 Apr 1999-14 Apr 2000
FRED HUTCHINSON CANCER RESEARCH CENTERSEATTLE WA
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Our previous studies in pubescent female rats suggested that nitrosomethylurea NMU mediated epigenetic effects on DNA conformation within the Ha-ras promoter contributes to mammary carcinogenesis. The DNA region affected by NMU includes a transcriptional element identical to Ha-ras response element HRE found in human Ha-ras promoter. To identify the trans-acting factors that bind to the HRE sequence in mammary cells, we employed sequence specific DNA affinity chromatography and amino acid sequencing by tandem mass spectroscopy. CARG box-binding factor A CBF-A is the major protein species in mammary cells that bind specifically to the rat and human HRE sequence with high affinities. Transient transfection as says using reporter plasmids verified that mutations within the HRE that disrupt binding of CBF-A, also reduced the activity of the rat Ha-ras promoter. Despite the fact that HRE element present in the Hasl promoter resembles a binding site for ets transcription factors, we did not detect the binding of ets related proteins. We demonstrated a correlation between HRE binding activity, induction of Ha-ras mRNA expression and cell cycle progression following serum stimulation in the mammary carcinoma cell line. Our results suggest that CBF-A plays an important role in regulation of Ha-ras promoter activity during mammary carcinogenesis.
- Anatomy and Physiology
- Medicine and Medical Research