Poster abstracts
Poster number 5 submitted by Sarah Choudury
Identification of A Novel Epigenetic Silencing Factor in Arabidopsis Thaliana
Sarah G. Choudury (MCDB, Department of Molecular Genetics), Kaushik Panda (Department of Molecular Genetics), Diego Cuerda Gil (Department of Molecular Genetics), Andrea McCue (Department of Molecular Genetics), Alissa Cullen (Department of Molecular Genetics)
Abstract:
In order to maintain genome integrity, fungi, plants, and animals modify transposable element (TE) chromatin to epigenetically repress TE activity. DNA methylation is critical for this epigenetic repression. Once established at TEs, DNA methylation can be propagated through cell divisions by methyltransferases. However, the mechanism by which DNA methylation and epigenetic silencing are originally targeted to TEs is not well understood. Our lab has identified a pathway in Arabidopsis that acts to direct de novo cytosine DNA methylation to transcriptionally active TEs, and is thus in part responsible for the initiation of silencing at these loci. This pathway utilizes endogenous 21-22 nucleotide (nt) small interfering RNAs (siRNAs) which result from the post-transcriptional degradation of TE mRNAs. The siRNAs direct Argonaute (AGO) proteins to chromatin which then triggers de novo DNA methylation. Previous studies from our lab genetically identified AGO6 as the key effector protein in this pathway. Because of AGO6’s key role in the initiation of silencing, we have focused on it and its interactors to better understand the pathway mechanism. Previous experiments in our lab utilized immunoprecipitation (IP) of AGO6 followed by mass spectrometry (MS) to identify AGO6-interacting proteins. We set out to discover novel silencing factors by screening through AGO6-interactors identified by IP-MS. For those factors that were found to play an important role in silencing, I aimed to understand their mode of action by performing molecular characterizations including whole genome methylation analysis, sRNA production assays, and AGO sRNA-loading assays. Using this approach we have identified a novel factor required for silencing initiation at TEs.
Keywords: Epigenetics, DNA Methylation, Transposable Elements