Date of Award


Degree Name

Biological Sciences


College of Science

Type of Degree


Document Type


First Advisor

Philippe Georgel

Second Advisor

Eric Blough

Third Advisor

Richard Niles

Fourth Advisor



The eukaryotic genome is organized into distinct domains with discrete regulatory potential, influenced by the variation in local chromatin structure. An example of chromatin-mediated consequences on gene expression is mating type determination of yeast Saccharomyces cerevisiae, which depends on silencing of specific gene cassettes. Silencing in yeast involves key proteins, amongst which the Silent Information Regulator (Sir) proteins are essential. Sir1p, Sir2p, and Sir4p are recruited to nucleate silencing events, while Sir3p serves as the pivotal factor in spreading the silent state. This investigation characterizes the DNA binding properties of Sir3p using DNA fragments with varying degrees of inherent flexibility, a characteristic that mimics nucleosomal and linker DNA. Sir3p binds to all DNA tested, but displays a higher affinity for linear DNA fragments, and even promotes formation of distinct DNA-protein complexes. Cumulatively, these results suggest the involvement of a DNA component in spreading of the silent state in Saccharomyces cerevisiae.


DNA-binding proteins.