Budding yeast uses a gene repression mechanism, known as silencing, to control the expression of key developmental regulatory genes. Silencing is distinguished from more commonly described modes of gene regulation in that the repression, once established, is a permanent, heritable property of the gene, known as an "epigenetic" effect. Similar gene silencing mechanisms underlie the development of all eukaryotes, including humans. To gain insights into the mechanism of epigenetic inheritance in yeast two specific questions will be addressed: First, what specific functions of the silencing machinery are required for epigenetic inheritance? The lab will create and characterize new dominant and conditional alleles of several silencing genes, including SIR2. Particular in vivo defects caused by these mutations will be correlated with alterations of Sir2's biochemical properties in vitro. Second, what is the role of chromosomal anchoring in establishing and inheriting the repressed state? The Sir4 and Rap1 silencing factors are known to localize to the nuclear periphery and act as anchors for the DNA sequences they bind, but the influence of chromosomal localization on gene expression is not clear. To examine the role of chromosomal anchoring on gene silencing the lab is using the yeast REP3 sequence as a surrogate anchor. This project will examine the ability of REP3 to substitute for the functions of known silencing factors, and investigate the possibility that the silencing and REP3 systems have common anchoring sites. The educational component of this CAREER award will support development of two undergraduate courses, Molecular Biology, designed for science majors, and Genetics: From Mendel to the Human Genome Project, designed for non-science majors.
