PRMT5- mediated symmetric arginine dimethylation is attenuated by mutant huntingtin and is impaired in Huntington's disease (HD).
Abnormal protein interactions of mutant huntingtin (Htt) triggered by polyglutamine expansion are thought to mediate Huntington's disease (HD) pathogenesis. Here, we explored a functional interaction of Htt with protein arginine methyltransferase 5 (PRMT5), an enzyme mediating symmetrical dimethylation of arginine (sDMA) of key cellular proteins, including histones, and spliceosomal Sm proteins. Gene transcription and RNA splicing are impaired in HD. We demonstrated PRMT5 and Htt interaction and their co-localization in transfected neurons and in HD brain. As a result of this interaction, normal (but to a lesser extend mutant) Htt stimulated PRMT5 activity in vitro. SDMA of histones H2A and H4 was reduced in the presence of mutant Htt in primary cultured neurons and in HD brain, consistent with a demonstrated reduction in R3Me2s occupancy at the transcriptionally repressed promoters in HD brain. SDMA of another PRMT5 substrate, Cajal body marker coilin, was also reduced in the HD mouse model and in human HD brain. Finally, compensation of PRMT5 deficiency by ectopic expression of PRMT5/MEP50 complexes, or by the knock-down of H4R3Me2 demethylase JMJD6, reversed the toxic effects of mutant Htt in primary cortical neurons, suggesting that PRMT5 deficiency may mediate, at least in part, HD pathogenesis. These studies revealed a potential new mechanism for disruption of gene expression and RNA processing in HD, involving a loss of normal function of Htt in facilitation of PRMT5, supporting the idea that epigenetic regulation of gene transcription may be involved in HD and highlighting symmetric dimethylation of arginine as potential new therapeutic target.
a Division of Neurobiology; Department of Psychiatry; Johns Hopkins University School of Medicine ; CMSC 8-121; Baltimore , MD , USA.
Tamara
T
Ratovitski
Nicolas
N
Arbez
Jacqueline C
JC
Stewart
Ekaterine
E
Chighladze
Christopher A
CA
Ross
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D044127:Epigenesis, Genetic / Q000502:physiology*; D005786:Gene Expression Regulation / Q000235:genetics*; D057809:HEK293 Cells; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D011484:Protein-Arginine N-Methyltransferases / Q000378:metabolism*; D051381:Rats
C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C487735:dimethylarginine; C068921:p80-coilin; D001120:Arginine; C400529:PRMT5 protein, human; D011484:Protein-Arginine N-Methyltransferases
BDNF, brain-derived neurotrophic factor; CB, Cajal body; ChIP, the chromatin immunoprecipitation; DMEM, Dulbecco's modified Eagle's medium; FBS, fetal bovine serum; HD, Huntington's disease; HEK, human embryonic kidney; Htt, huntingtin; Huntington's disease mechanism; IP, immunoprecipitation; IgG, immunoglobulin; PIC, protease inhibitors cocktail; PRMT5, protein arginine methyltransferase; RNA processing; SMN, survival of motor neurons; Sm proteins, spleceosomal small nuclear ribonucleoproteins; gene transcription; huntingtin; neurodegeneration; polyQ, polyglutamine; protein interactions; protein methylation; sDMA, symmetrical arginine dimethylation; snRNPs, small nuclear ribonucleoprotein particles