Initiation of transcription is the most important step in gene expression. Without the initiation of transcription, and the subsequent transcription of the gene into mRNA by RNA polymerase, the phenotype controlled by the gene will not be seen. Therefore in depth studies have revealed much about what is needed for transcription to begin.
The control of transcription is an integrated mechanism involving cis-acting sequences and trans-acting factors. Cis-acting sequence usually lies 5' of the transcriptional start site. These sequences are the substrate for trans-acting factors. These factors bind to the cis-acting sequences and prepare the DNA in their vicinity for transcription. Because the trans-acting factors are proteins, they must also be encoded by genes. And these genes may also be controlled the interaction of cis-acting sequences and trans-acting factors. This interplay between genes and their cis-acting sequences and trans-acting factors is a cascade of genetic events.
Copyright © 1997. Phillip McClean