In the 3153A strain, a gene called SIR2 (for silent information regulator), which seems to be important for phenotypic switching, has been found. SIR2 was originally found in Saccharomyces cerevisiae (brewer's yeast), where it is involved in chromosomal silencing —a form of transcriptional regulation , in which regions of the genome are reversibly inactivated by changes in chromatin structure (chromatin is the complex of DNA and proteins that make chromosomes ). In yeast, genes involved in the control of mating type are found in these silent regions, and SIR2 represses their expression by maintaining a silent-competent chromatin structure in this region. The discovery of a C. albicans SIR2 implicated in phenotypic switching suggests it, too, has silent regions controlled by SIR2 , in which the phenotype-specific genes may reside. How SIR2 itself is regulated in S. cerevisiae may yet provide more clues as to the switching mechanisms of C. albicans .
No heart-related essay on athletes would be complete without mentioning performance-enhancing drugs. No longer are these agents confined to professional athletes. Numerous reports in the media have documented the use of anabolic steroids, erythropoietic stimulants (EPO), insulin, human growth hormone and pseudo-ephedrine in amateur athletes. Few scientific studies have been done, as finding athletes who admit to taking illegal substances is challenging, but it is well known that all of these drugs have potentially negative effects on the heart. I’m not pointing fingers here; the authors of the Circulation review, along with most reviews on the athletic heart mention performance-enhancing drugs.