title: Identification of Multiple Proteins Coupling Transcriptional Gene Silencing to Genome Stability in Arabidopsis thaliana.
abstract: Eukaryotic genomes are regulated by epigenetic marks that act to modulate transcriptional control as well as to regulate DNA replication and repair. In Arabidopsis thaliana, mutation of the ATXR5 and ATXR6 histone methyltransferases causes reduction in histone H3 lysine 27 monomethylation, transcriptional upregulation of transposons, and a genome instability defect in which there is an accumulation of excess DNA corresponding to pericentromeric heterochromatin. We designed a forward genetic screen to identify suppressors of the atxr5/6 phenotype that uncovered loss-of-function mutations in two components of the TREX-2 complex (AtTHP1, AtSAC3B), a SUMO-interacting E3 ubiquitin ligase (AtSTUbL2) and a methyl-binding domain protein (AtMBD9). Additionally, using a reverse genetic approach, we show that a mutation in a plant homolog of the tumor suppressor gene BRCA1 enhances the atxr5/6 phenotype. Through characterization of these mutations, our results suggest models for the production atxr5 atxr6-induced extra DNA involving conflicts between the replicative and transcriptional processes in the cell, and suggest that the atxr5 atxr6 transcriptional defects may be the cause of the genome instability defects in the mutants. These findings highlight the critical intersection of transcriptional silencing and DNA replication in the maintenance of genome stability of heterochromatin.
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America.|Center for Precision Diagnostics, University of Washington, Seattle, Washington, United States of America.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hale
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America.
authors.forename: Magdalena E
authors.initials: ME
authors.lastname: Potok
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lopez
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America.
authors.forename: Truman
authors.initials: T
authors.lastname: Do
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America.
authors.forename: Ao
authors.initials: A
authors.lastname: Liu
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America.
authors.forename: Javier
authors.identifier: 0000-0003-2225-7168
authors.initials: J
authors.lastname: Gallego-Bartolome
authors.affiliation: Department of Biology, Indiana University, Bloomington, Indiana, United States of America.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Michaels
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America.|Howard Hughes Medical Institute, University of California at Los Angeles, Los Angeles, California, United States of America.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Jacobsen
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics*; D020169:Caspases / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D020868:Gene Silencing / Q000502:physiology*; D042822:Genomic Instability / Q000235:genetics*; D006570:Heterochromatin / Q000235:genetics; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics; D008780:Methyltransferases / Q000235:genetics; D009154:Mutation / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: D029681:Arabidopsis Proteins; D006570:Heterochromatin; C542364:ATXR5 protein, Arabidopsis; C542365:ATXR6 protein, Arabidopsis; D000076983:Histone Methyltransferases; D008780:Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D020169:Caspases; C554451:MC1 protein, Arabidopsis