Poster abstracts
Poster number 24 submitted by Anna Hu
Looking into the internal coordination within the ASAP complex for gene regulation in Arabidopsis
Anna Hu (Biochemistry Program, Department of Biology), Xiao-Ning Zhang (Biochemistry Program, Department of Biology)
Abstract:
An important event in gene expression is the covalent modification of histone proteins. In eukaryotic cells, the Sin3-associated protein 18 (SAP18) can recruit histone deacetylase to repress target gene transcription. In Arabidopsis thaliana, an existing model suggests that SAP18 interacts with other RNA binding proteins, RNPS1 and apoptotic chromatin condensation inducer in the nucleus (Acinus), to form the conserved apoptosis and splicing-associated protein (ASAP) complex at the promoter of the FLOWER LOCUS C (FLC) gene for silencing. Besides transcriptional regulation, the ASAP complex also affects splicing and nonsense mediated decay by binding to exon junction complexes. In Arabidopsis, a null mutation in the RNPS1 ortholog, Serine/Arginine-rich 45 (SR45), has been found to cause an increased expression in a set of genes including FLC and a substantial decrease in nuclear SAP18 protein. Questions remain as to whether some of these more actively transcribed genes in the sr45-1 mutant are targets for SAP18-mediated gene silencing. To answer this question, the activity of SAP18 at the chromatin level was investigated by ChIP-seq assay using translational fusion SAP18pro::SAP18-GFP transgenic plants in the wild type background. A comparison between SAP18-associated DNA regions and SR45-differentially regulated genes revealed that some SAP18-associated sequences were in the promoter region of SR45-differentially expressed genes indicating a possible role of SAP18 in regulating the transcription of these genes, which may help explain some of the observed phenotypes of the sr45-1 mutant. More interestingly, SAP18-associated sequences were also identified in exonic and/or intronic regions. In order to understand the effects of targeting different parts of the gene body, further investigation will be conducted.
References:
Zhang, X., Shi, Y., Powers, J. J., Gowda, N. B., Zhang, C., Ibrahim, H. M., . . . Mount, S. M. (2017). Transcriptome analyses reveal SR45 to be a neutral splicing regulator and a suppressor of innate immunity in Arabidopsis thaliana. BMC Genomics, 18(1). doi:10.1186/s12864-017-4183-7
Questa, J. I., Song, J., Geraldo, N., An, H., Dean, C. (2016). Arabidopsis transcriptional repressor VAL1 triggers Polycomb silencing at FLC during vernalization. Science, 353(6298), 485-488. doi:10.1126/science.aaf7354
Keywords: SAP18, ASAP complex , transcriptional regulation