Nuclear factors from expressing tissues interact in vitro with a rat alpha-2u globulin gene intron

Members of the rat alpha 2u globulin gene family are expressed in a tissue-specific manner. Using a DNase I footprinting assay, we find that expressing tissues (liver, lachrymal, and salivary gland) contain nuclear proteins that interact specifically with two sites in the third intron of a cloned gene. These sequences are similar to a CCAAT-like sequence in the 5'-flanking region of the gene and the binding site for the transcription factor Sp1. Extracts of nonexpressing tissues (kidney, testis, brain, and spleen) do not show footprinting activity at these sites. Whereas hepatic expression of alpha 2u globulin is restricted to normal adult males, nuclear extracts of liver from all animals (adult and juvenile, male and female, intact and hypophysectomized) produce similar footprints. Footprints by extracts of lachrymal and salivary glands, tissues that express a subset of alpha 2u globulin genes distinct from the hepatic set, are also similar to the liver activity. The findings suggest that the third intron of an alpha 2u globulin gene contains sites that interact with tissue-specific factors to establish the potential for hormonal and developmental control of expression.