Mechanism of Extinction of Growth Hormone and Prolactin Genes in Somatic Cell Hybrids

Abstract

Two major unanswered questions exist regarding the nature of steroid regulation of genes. First, how is it that steroid hormones act on the genome of differentiated cells programmed to respond to them in a particular way? A common end result of this effect is the accumulation of specific mRNA sequences. Second, what are the controls that dictate whether a tissue responds to a particular hormone at all and, if so, which of many tissue-specific effects the hormone elicits? Earlier, it was believed that the presence or absence of specific steroid receptors in various cells might be the answer, but virtually every cell type in the body contains glucocorticoid receptors. It may be, of course, that there are subtle differences in the glucocorticoid receptors in different cell types, or as is more popularly believed, there may be control molecules that organize the DNA in different differentiated cells so as to prevent the expression or induction of unwanted genes.