An Tyrrell

POLYMORPHISMS IN NON-CODING REGIONS LEAD TO DIFFERENTIAL GENE EXPRESSION. An Tyrrell¹, Justin Fay², Biology Department, Washington University, Saint Louis, MO¹, Genetics Department, Washington University Medical School, Saint Louis, MO²

Microarray studies have shown that a large number of genes are differentially expressed within natural populations. This leads to the question of whether differences in gene expression have any effect on function. To answer this question, we must first determine what the genetic basis is for the observed expression differences.

Previous work identified approximately 100 single nucleotide polymorphisms associated with five genes and found that two of those genes, MLS1 and PDR10, showed a higher rate of polymorphism in the non-coding promoter regions than the synonymous sites. In order to test whether this high rate of polymorphism has any regulatory function, we cloned the promoter region of MLS1 of ten different strains of yeast into a Beta-gal reporter construct. Then we tested each construct for expression differences in 2% and 0.2% glucose. Our results showed that five strains had high levels of expression, one strain seemed to be intermediate, and two strains showed low levels of expression.

In order to determine whether a specific allele is responsible for these differences, we used one high, one intermediate, and one low expression strain and mutated three polymorphic sites to test if the expression changes. Currently we are testing expression levels and verifying the sequence of the mutated promoter region. In addition, we are also cloning fourteen different strains of PDR10 in order to determine whether it also exhibits different expression levels.