title: Arabidopsis RPT2a, 19S proteasome subunit, regulates gene silencing via DNA methylation.
abstract: The ubiquitin/proteasome pathway plays a crucial role in many biological processes. Here we report a novel role for the Arabidopsis 19S proteasome subunit RPT2a in regulating gene activity at the transcriptional level via DNA methylation. Knockout mutation of the RPT2a gene did not alter global protein levels; however, the transcriptional activities of reporter transgenes were severely reduced compared to those in the wild type. This transcriptional gene silencing (TGS) was observed for transgenes under control of either the constitutive CaMV 35S promoter or the cold-inducible RD29A promoter. Bisulfite sequencing analysis revealed that both the transgene and endogenous RD29A promoter regions were hypermethylated at CG and non-CG contexts in the rpt2a mutant. Moreover, the TGS of transgenes driven by the CaMV 35S promoters was released by treatment with the DNA methylation inhibitor 5-aza-2'-deoxycytidine, but not by application of the inhibitor of histone deacetylase Trichostatin A. Genetic crosses with the DNA methyltransferase met1 single or drm1drm2cmt3 triple mutants also resulted in a release of CaMV 35S transgene TGS in the rpt2a mutant background. Increased methylation was also found at transposon sequences, suggesting that the 19S proteasome containing AtRPT2a negatively regulates TGS at transgenes and at specific endogenous genes through DNA methylation.
authors.affiliation: Faculty of Science and Graduate School of Life Science, Hokkaido University, Sapporo, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Sako
authors.forename: Yuko
authors.initials: Y
authors.lastname: Maki
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kanai
authors.forename: Eriko
authors.initials: E
authors.lastname: Kato
authors.forename: Shugo
authors.initials: S
authors.lastname: Maekawa
authors.forename: Shigetaka
authors.initials: S
authors.lastname: Yasuda
authors.forename: Takeo
authors.initials: T
authors.lastname: Sato
authors.forename: Masaaki K
authors.initials: MK
authors.lastname: Watahiki
authors.forename: Junji
authors.initials: J
authors.lastname: Yamaguchi
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D020868:Gene Silencing; D006655:Histone Deacetylases / Q000378:metabolism; D009154:Mutation; D011401:Promoter Regions, Genetic; D046988:Proteasome Endopeptidase Complex / Q000235:genetics*; D014158:Transcription, Genetic; D019076:Transgenes / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; C487429:RPT2a protein, Arabidopsis; D046988:Proteasome Endopeptidase Complex; D006655:Histone Deacetylases