FIG. 4.

Active Stat5a and Stat5b homodimers in lactating mammary glands. Nuclear protein extracts from mammary glands lactating for 10 days were immunodepleted of Stat5a or Stat5b as indicated. A 6-μg amount of immunodepleted (immunodepl.) extracts was analyzed by EMSA either in the absence (control [C]) or in the presence of Stat5a or Stat5b antiserum as indicated. Stat5a- or Stat5b-DNA complexes are indicated by arrows on the right side. Immunodepleted extracts gave a background band which masked the Stat5a and Stat5b supershifts. The electrophoretic mobility of the Stat-DNA complex from nonimmunodepleted nuclear extract is shown in lane 1.