April 26 2007
12:00 LSB 2320

Abstract:

Eukaryotic genomes vary greatly in size, though this variance is largely due to repeats and not gene number. Repetitive elements are commonly found in heterochromatic regions where they are epigenetically silenced through modifications such as cytosine and histone methylation.

Understanding the process by which repeats versus genes are recognized is an important question in genome biology. Recent work has implicated siRNA generated by the RNAinterference pathway as being key specificity determinants for silencing of repeats. We have used Arabidopsis thaliana to genetically dissect small RNA metabolism and test the extent to which siRNA target DNA methylation. Ultimately, these siRNA act through the de novo DNA methyltransferase DRM2, whose distribution and mechanism we are also studying. Interestingly, we have found that plants and mammals have convergently evolved catalytically inactive partner proteins that function in control of DNA methylation. Finally we are investigating endogenous loci that are silenced by DRM2 to better understand its targeting and role in gene regulation.