Talk abstracts

Talk on Wednesday 09:45-10:00am submitted by Tami Coursey

Characterization of plant histone readers EML1 and EML3 and their interaction with geminiviruses

Tami Coursey (Molecular Genetics, Ohio State University), Jelena Brkljacic (Arabidopsis Biological Resource Center, Ohio State University), Erich Grotewold (Molecular Genetics, Ohio State University), David M. Bisaro (Molecular Genetics, Ohio State University)

Abstract:
Geminiviruses replicate ssDNA genomes through dsDNA intermediates that associate with cellular histones to form mini-chromosomes. We previously showed viral mini-chromosomes can be targeted for repressive cytosine methylation and can acquire repressive histone methylation (e.g. di-methylated lysine 9 on Histone H3, H3K9me2). Conversely, viral genomes lacking cytosine methylation are often associated with active histone marks (e.g. Histone H3 acetylated at lysine 9/14, H3Ac). While components involved in histone post-translational modification in plants are relatively well characterized, less is known about the proteins that read these epigenetic marks. Histone reader proteins bind specific histone modifications to maintain and/or spread a modification, and can alter gene expression by recruiting specific nucleosome remodeling complexes and transcription factors. Using geminiviruses as models to identify and characterize plant chromatin readers, we hypothesize EMSY LIKE (EML) proteins 1 & 3 are plant histone readers. EML1 and EML3 contain Agenet domains homologous to known histone reader domains (Tudor domains). Initial studies tested whether these proteins interact with histones and geminivirus genomes. To date, eml1 and eml3 Arabidopsis plants display either hypersusceptibility or increased tolerance to Cabbage leaf curl virus (CaLCuV) compared to wild-type plants. Differences in symptoms correlate with changes in viral DNA levels, as measured by qPCR analysis. Using chromatin immunoprecipitation (ChIP) we have also observed changes in H3K9me2 and H3K9Ac levels associated with CaLCuV genomes in mutant plants. Co-immunoprecipitation and ChIP experiments further indicate EML1 and EML3 associate with histone H3 and the CaLCuV genome. These results suggest Agenet domain-containing EML proteins are histone readers and play specific roles in promoting virus infection or bolstering plant antiviral defense pathways.

References:
1. Raja P, Sanville BC, Buchmann RC & DM Bisaro. (2008). Viral genome methylation as an epigenetic defense against geminiviruses. J Virol. 82(18):8997-9007.

2. Mauer-Stroh S, Dickens NJ, Hughes-Davies L, Kouzarides T, Eisenhaber F & CP Ponting. (2003). The Tudor domain ‘Royal Family’: Tudor, plant Agenet, Chromo, PWWP and MBT domains. Trends Biochem Sci. 28(2):69-74.

Keywords: Chromatin, Geminiviruses, Molecular Virolgoy