Define role of Zinc in controlling Gene Expression?
Zinc atoms have specific structural roles in enzyme molecules, as well as, in many other proteins and in bio membranes. These structural roles of zinc are ubiquitous and of outstanding importance in cellular and sub-cellular metabolism. One outstanding example that has generated a great deal of is the zinc finger motif, the most common recurring motif in transcription proteins. The configuration of these "fingers," which determines their binding to DNA, is determined by the single zinc action at their base. The linking of these zinc fingers to corresponding sites on DNA initiates the transcription process and gene expression. Similar motifs have been identified in nuclear hormonal receptors, including those for oestrogen, testosterone and vitamin D.
Zinc, you might recall studying earlier in this course, plays an important role in the maintenance of the immune system. While the mechanisms of zinc ions interaction with immune cells are still poorly understood, a striking concurrent effect of zinc is the induction of the biosynthesis of metallothioneins (Mi"), a group of low molecular weight, cysteine-rich metal-binding proteins, believed to play a role in zinc homeostasis.
Dc Cousins was the first, in the late 1970s, to elucidate the presence of intestinal metallothionein, a protein involved in the regulation and kinetics of the intestinal absorption of dietary zinc, while also discovering its vital role in cellular zinc metabolism,
its relationship to zinc deficiency and the consequences that can have on the body. In his studies, he was the first to demonstrate that a dietary trace mineral could actually influence the transcriptional regulation of gene expression.
The subsequent discovery and understanding of the zinc-binding properties of another protein - cysteine-rich intestinal protein or CRIP - has led to a more complete appreciation of how zinc behaves in intestinal and immune cells. CRIP is now understood to have a role in immune defence against infection. Most recently, the discovery by Dc Cousins that zinc deficiencies can actually induce the expression of an intestinal honnone called uroguanylin is a breakthrough toward realizing the probable role that zinc deficiencies may play in zinc-responsive diarrhoea1 diseases common in young children, particularly in the developing world. Finally, let us study about the role played by vitamins in controlling gene expression.