title: Methylation of histone H3 and H4 by PRMT5 regulates ribosomal RNA gene transcription.
abstract: In an effort to understand the epigenetic regulation of ribosomal RNA gene (rDNA) expression we have previously demonstrated the role of DNA methyltransferases and methyl CpG binding proteins in rRNA synthesis. Here, we studied the role of protein arginine methyltransferase PRMT5 and the two methylated histones H3R8Me2 and H4R3Me2, in rDNA expression in Epstein Barr virus- transformed primary B-cells (LCLs) and in HeLa cells responding to serum-regulated growth. Chromatin immunoprecipitation assay showed that histones H3 and H4 associated with rRNA promoters were differentially methylated at arginine residues 8 and 3, respectively, depending on its transcriptional activity. Association of PRMT5 and methylated H3 with the unmethylated promoters in resting B-cells was significantly reduced in rapidly growing LCLs. Unlike PRMT5 and H3R8Me2, histone H4 associated with both methylated and unmethylated rRNA promoters in resting B-cells was methylated at the R3 residue. However, a dramatic decrease in R3 methylation of H4 recruited to the unmethylated rRNA promoters was observed in LCLs while it remained unaltered in the fraction bound to the methylated promoters. Differential interaction of PRMT5 and methylation of H3 and H4 associated with the rRNA promoters was also observed when serum starved HeLa cells were allowed to grow in serum replenished media. Ectopic expression of PRMT5 suppressed activity of both unmethylated and methylated rRNA promoter in transient transfection assay whereas siRNA mediated knockdown of PRMT5 increased rRNA synthesis in HeLa cells. These data suggest a key role of PRMT5 and the two methylated histones in regulating rRNA promoter activity.
authors.affiliation: Department of Molecular and Cellular Biochemistry, Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Sarmila
authors.initials: S
authors.lastname: Majumder
authors.forename: Lapo
authors.initials: L
authors.lastname: Alinari
authors.forename: Satavisha
authors.initials: S
authors.lastname: Roy
authors.forename: Tyler
authors.initials: T
authors.lastname: Miller
authors.forename: Jharna
authors.initials: J
authors.lastname: Datta
authors.forename: Said
authors.initials: S
authors.lastname: Sif
authors.forename: Robert
authors.initials: R
authors.lastname: Baiocchi
authors.forename: Samson T
authors.initials: ST
authors.lastname: Jacob
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D019175:DNA Methylation; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism*; D006801:Humans; D008745:Methylation; D051379:Mice; D016513:Mice, SCID; D011496:Protein Methyltransferases / Q000235:genetics / Q000378:metabolism*; D011484:Protein-Arginine N-Methyltransferases; D012335:RNA, Ribosomal / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D006657:Histones; D012335:RNA, Ribosomal; D011496:Protein Methyltransferases; C400529:PRMT5 protein, human; D011484:Protein-Arginine N-Methyltransferases