Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/1998
Publication Date: N/A
Citation: Interpretive Summary: Interpretive Summary not needed for this 115.
Technical Abstract: The mechanism of insulin-stimulated milk protein gene transcription is unknown. Studies on the fatty acid synthase gene suggest that USF is an insulin-responsive transcription factor. Electrophoretic mobility shift assays were used to test the hypothesis that the USF found in mammary gland nuclear extracts is both developmentally and hormonally regulated. Analysis of USF binding activity in nuclear extracts isolated from virgin, pregnant, lactating and involuting mice mammary glands showed that USF binding activity is elevated at 10 days of lactation. Western blot analysis indicated that USF-1 and USF-2 proteins were expressed in lactating mammary glands, but not during involution. These results suggest that USF protein expression and DNA binding activity are elevated in differentiated mammary epithelial cells. To confirm these findings in vitro, HC11 clonal mammary epithelial cell lines were induced to differentiate in the presence of dexamethasone (D), insulin (I), and prolactin (P). USF protein was detected only in the presence of DP or DIP. However, USF-1 binding activity was elevated only in the present of DIP. Beta-casein mRNA was detected only in the presence of DIP. Taken together, the results support the hypothesis that USF regulated mammary epithelial cell differentiation. (Supported by USDA grant under Cooperative Agreement 58-6250-6-001).