Chapter 1 - DNA sequences, transcription factors and chromatin structure

Abstract

The fundamental dogma of molecular biology is that DNA produces RNA, which in turn produces protein. If the genetic information which individual inherits as DNA is to be converted into the proteins that produce the corresponding characteristics of the individual, it must first be converted into an RNA product. The process of transcription whereby an RNA product is produced from the DNA is therefore an essential element in gene expression. The failure of this process to occur will obviously render redundant all the other steps that follow the production of the initial RNA transcript in eukaryotes, such as RNA splicing, transport to the cytoplasm or translation into protein. The central role of transcription in the process of gene expression also renders it an attractive control point for regulating the expression of genes in particular cell types or in response to a particular signal. Indeed it is now clear that in the vast majority of cases where a particular protein is produced only in a particular tissue or in response to a particular signal this is achieved by control processes, which ensure that its corresponding gene is transcribed only in that tissue or in response to such a signal. The genes encoding the immunoglobulin heavy and light chains of the antibody molecule are transcribed at high level only in the antibody producing B cells whilst the increase in somatostatin production in response to treatment of cells with cyclic AMP is mediated by increased transcription of the corresponding gene. Therefore, while posttranscriptional regulation affecting, for example, RNA splicing or stability plays some role in the regulation of gene expression.