title: Arabidopsis MAS2, an Essential Gene That Encodes a Homolog of Animal NF-κ B Activating Protein, Is Involved in 45S Ribosomal DNA Silencing.
abstract: Ribosome biogenesis requires stoichiometric amounts of ribosomal proteins and rRNAs. Synthesis of rRNAs consumes most of the transcriptional activity of eukaryotic cells, but its regulation remains largely unclear in plants. We conducted a screen for ethyl methanesulfonate-induced suppressors of Arabidopsis thaliana ago1-52, a hypomorphic allele of AGO1 (ARGONAUTE1), a key gene in microRNA pathways. We identified nine extragenic suppressors as alleles of MAS2 (MORPHOLOGY OF AGO1-52 SUPPRESSED2). Positional cloning showed that MAS2 encodes the putative ortholog of NKAP (NF-κ B activating protein), a conserved eukaryotic protein involved in transcriptional repression and splicing in animals. The mas2 point mutations behave as informational suppressors of ago1 alleles that cause missplicing. MAS2 is a single-copy gene whose insertional alleles are embryonic lethal. In yeast two-hybrid assays, MAS2 interacted with splicing and ribosome biogenesis proteins, and fluorescence in situ hybridization showed that MAS2 colocalizes with the 45S rDNA at the nucleolar organizer regions (NORs). The artificial microRNA amiR-MAS2 partially repressed MAS2 and caused hypomethylation of 45S rDNA promoters as well as partial NOR decondensation, indicating that MAS2 negatively regulates 45S rDNA expression. Our results thus reveal a key player in the regulation of rRNA synthesis in plants.
authors.affiliation: Instituto de Bioingeniería, Universidad Miguel Hernández, 03202 Elche, Alicante, Spain.
authors.forename: Ana Belén
authors.identifier: http://orcid.org/0000-0002-1315-8400
authors.initials: AB
authors.lastname: Sánchez-García
authors.affiliation: Instituto de Bioingeniería, Universidad Miguel Hernández, 03202 Elche, Alicante, Spain.
authors.forename: Verónica
authors.identifier: http://orcid.org/0000-0003-3885-6624
authors.initials: V
authors.lastname: Aguilera
authors.affiliation: Instituto de Bioingeniería, Universidad Miguel Hernández, 03202 Elche, Alicante, Spain.
authors.forename: Rosa
authors.identifier: http://orcid.org/0000-0001-9389-2906
authors.initials: R
authors.lastname: Micol-Ponce
authors.affiliation: Instituto de Bioingeniería, Universidad Miguel Hernández, 03202 Elche, Alicante, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Jover-Gil
authors.affiliation: Instituto de Bioingeniería, Universidad Miguel Hernández, 03202 Elche, Alicante, Spain mrponce@umh.es.
authors.forename: María Rosa
authors.identifier: http://orcid.org/0000-0003-0770-4230
authors.initials: MR
authors.lastname: Ponce
mesh_terms: D000483:Alleles; D000818:Animals; D017360:Arabidopsis / Q000196:embryology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D056970:Co-Repressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017124:Conserved Sequence; D019175:DNA Methylation / Q000235:genetics; D021901:DNA, Intergenic; D004275:DNA, Ribosomal / Q000235:genetics*; D004843:Epistasis, Genetic; D020868:Gene Silencing; D020043:Genes, Essential; D016153:Genes, Suppressor; D058685:Genetic Pleiotropy; D006801:Humans; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry; D009697:Nucleolus Organizer Region / Q000378:metabolism; D010641:Phenotype; D011485:Protein Binding; D021381:Protein Transport; D012326:RNA Splicing / Q000235:genetics; D012097:Repressor Proteins; D012639:Seeds / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism; D013489:Suppression, Genetic; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D056970:Co-Repressor Proteins; D021901:DNA, Intergenic; D004275:DNA, Ribosomal; C000607689:MAS2 protein, Arabidopsis; C479077:NKAP protein, human; D009687:Nuclear Proteins; D012097:Repressor Proteins