Identification of nuclear proteins that bind to the glucocorticoid regulatory region of a rat alpha 2u-globulin gene.

The induction of rat alpha 2u-globulin by glucocorticoids is a secondary response to the hormone, that is protein synthesis is absolutely required for induction. Using the DNase I protection assay, we have identified three proteins present in rat liver nuclei that bind in or near the regulatory region of a cloned alpha 2u-globulin gene. One protein which we term alpha 2u-globulin nuclear factor 1 (alpha 2uNF1), binds to precisely the sequence we have previously shown to be required for hormonal induction. Genes containing linker-scanning mutations in this region show diminished binding to this nuclear factor and display greatly reduced or abolished glucocorticoid response. alpha 2uNF1 was detected in nuclei from several sources, and its level is apparently unaffected by glucocorticoids. Its recognition sequence is unlike those of previously reported transcription factors. We detect two other proteins, alpha 2uNF2 and alpha 2uNF3, that bind near the alpha 2u-globulin regulatory region. A mutant alpha 2u-globulin promoter which does not bind alpha 2uNF2 shows increased inducibility by glucocorticoids in transfected mouse L-cells. The binding of alpha 2uNF3 is not required for alpha 2u-globulin induction by the hormone.