REGULATION OF GENE TRANSCRIPTION BY BOTANICALS: Novel Regulatory Mechanisms

Early investigations of gene regulation revealed that nutrients could modulate gene expression, an example being the discovery of metal-regulated gene transcription (11, 19, 44). Only more recently have we focused on the ability of non-nutritional botanicals or functional food components to affect gene expression at the transcriptional level. Significant findings include the discovery that hyperforin is an active ingredient of the herbal remedy St. John's wort, and activates gene transcription of cytochrome p450-3A4, causing significant botanical-drug interactions. Recently, the lipid-regulating peroxisome proliferator-activated receptors have been studied as receptors activated by soy isoflavones, perhaps explaining the lipid-lowering effect of soy intake. Epigallocatechin gallate has been shown to be an inhibitor of the protealytic activity of the proteasome; this inhibition has a significant implication for cell proliferation and the stability of transcription factors in the nucleus. Very recently, the effects of botanicals have been studied as activators of sirtuins, important deacetylation enzymes that have been shown to enhance lifespan in a variety of organisms. Sirtuins have been implicated in the lifespan-enhancing effect of caloric restriction. Originally presumed to act mainly on compaction or accessibility of DNA, recent evidence shows important activity of sirtuins as controllers of transcriptional coactivator availability. This review focuses on novel mechanisms by which botanical products regulate cell function via gene transcription. Investigating these newly appreciated mechanisms will assist with the characterization and clarification of specific effects of botanicals on gene expression.