ABSTRACT
As discussed in Chapter 7, the expression of specific genes in particular cell types or tissues is regulated by DNA sequence motifs present within promoter or enhancer elements which control the alteration in chromatin structure of the gene that occurs in a particular lineage, or the subsequent induction of gene transcription. It was assumed for many years that such sequences would act by binding a regulatory protein which was only synthesized in a particular tissue or was present in an active form only in that tissue. In turn, the binding of this protein would result in the observed effect on gene expression. Indeed, as described in Section 7.2 cell extracts can be used in DNA mobility shift or DNase I footprinting assays to show that they contain protein(s) able to bind to a specific sequence.
