Ectopic expression of a polyalanine expansion mutant of poly(A)-binding protein N1 in muscle cells in culture inhibits myogenesis.
Oculopharyngeal muscular dystrophy (OPMD) is an adult-onset dominant genetic disease caused by the expansion of a GCG trinucleotide repeat that encodes the polyalanine tract at the N-terminus of the nuclear poly(A)-binding protein (PABPN1). Presence of intranuclear inclusions (INIs) containing PABPN1 aggregates in the skeletal muscles is the hallmark of OPMD. Here, we show that ectopic expression of the mutant PABPN1 produced INIs in a muscle cell culture model and reduced expression of several muscle-specific proteins including alpha-actin, slow troponin C, muscle creatine kinase, and two myogenic transcription factors, myogenin and MyoD. However, the levels of two upstream regulators of the MyoD gene, the Myf-5 and Pax3/7, were not affected, but both proteins co-localized with the PABPN1 aggregates in the mutant PABPN1 overexpressing cells. In these cells, although myogenin and MyoD levels were reduced, these two transcription factors did not co-localize with the mutant PABPN1 aggregates. Therefore, sequestration of Myf5 and Pax3/7 by the mutant PABPN1 aggregates was a specific effect on these factors. Our results suggest that trapping of these two important myogenic determinants may interfere with an early step in myogenesis.
Wang
Qishan
Q
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ont., Canada N1G 2W1.
Bag
Jnanankur
J
D000185:Actinin / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000378:metabolism; D009132:Muscles / Q000378:metabolism*; D039141:Muscular Dystrophy, Oculopharyngeal / Q000378:metabolism; D009154:Mutation; D017570:MyoD Protein / Q000378:metabolism; D051787:Myogenic Regulatory Factor 5 / Q000378:metabolism; D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor / Q000378:metabolism; D051761:Paired Box Transcription Factors / Q000378:metabolism; D010455:Peptides / Q000737:chemistry*; D039122:Poly(A)-Binding Protein I / Q000378:metabolism; D039102:Poly(A)-Binding Proteins / Q000737:chemistry* / Q000502:physiology; D014162:Transfection; D019209:Troponin C / Q000378:metabolism
C497417:MYF5 protein, human; D017570:MyoD Protein; D051787:Myogenic Regulatory Factor 5; C467335:PABPC3 protein, human; D000072041:PAX3 Transcription Factor; C489409:PAX3 protein, human; D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human; D051761:Paired Box Transcription Factors; D010455:Peptides; D039122:Poly(A)-Binding Protein I; D039102:Poly(A)-Binding Proteins; D019209:Troponin C; D000185:Actinin; D049452:Green Fluorescent Proteins; C019529:polyalanine