The Southwestern Assay

Determination of cellular phenotypes results from the expression of a limited number of genes whose products interact to establish a unique environment. The mechanisms by which individual cells can selectively express only a few of all the genes in a specific cell have been the focus of intense research during the last 10 yr. It has become apparent that developmental, tissue-specific, and hormone-regulated gene expression is, for the most part, controlled at the level of transcriptional initiation. This involves the interaction of specific DNA binding proteins with control elements present in the gene promoters. To better understand the process of gene transcription, characterization of these DNA binding proteins is a mandatory step.