Abstract:

Gene expression is the biological process in which DNA is transcribed to RNA that is then translated into proteins. A major puzzle in biology is how gene expression is controlled. An example is steroid-mediated gene expression, where steroid molecules bind to freely floating receptors in the cell that then attach to specific sites on the DNA and activate the gene expression process. The classical view is that gene expression involves the sequential assembly of a large complex of molecules called transcription factors on the DNA. The amount of protein produced in steroid-mediated gene expression is a monotonically increasing rational linear function of the amount of steroid present. This functional relationship is sometimes called a Michaelis-Menten function or a first order Hill function. However, one can show mathematically that the amount of protein produced in a biochemical reaction sequence of complex-building steps will not in general take rational linear form. I will show, using simple ideas from group theory, how a rational linear function can arise in a biologically plausible theory of steroid-mediated gene expression. They theory can make quantitative predictions for how various transcription factors can affect gene expression and assign a relative order to their actions.