title: Cotranslational association of mRNA encoding subunits of heteromeric ion channels.
abstract: Oligomers of homomeric voltage-gated potassium channels associate early in biogenesis as the nascent proteins emerge from the polysome. Less is known about how proteins emerging from different polysomes associate to form hetero-oligomeric channels. Here, we report that alternate mRNA transcripts encoding human ether-à-go-go-related gene (hERG) 1a and 1b subunits, which assemble to produce ion channels mediating cardiac repolarization, are physically associated during translation. We show that shRNA specifically targeting either hERG 1a or 1b transcripts reduced levels of both transcripts, but only when they were coexpressed heterologously. Both transcripts could be copurified with an Ab against the nascent hERG 1a N terminus. This interaction occurred even when translation of 1b was prevented, indicating the transcripts associate independent of their encoded proteins. The association was also demonstrated in cardiomyocytes, where levels of both hERG transcripts were reduced by either 1a or 1b shRNA, but native KCNE1 and ryanodine receptor 2 (RYR2) transcripts were unaffected. Changes in protein levels and membrane currents mirrored changes in transcript levels, indicating the targeted transcripts were undergoing translation. The physical association of transcripts encoding different subunits provides the spatial proximity required for nascent proteins to interact during biogenesis, and may represent a general mechanism facilitating assembly of heteromeric protein complexes involved in a range of biological processes.
authors.affiliation: Department of Neuroscience, Wisconsin Institutes of Medical Research, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705;
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.affiliation: Department of Neuroscience, Wisconsin Institutes of Medical Research, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705;
authors.forename: David K
authors.initials: DK
authors.lastname: Jones
authors.affiliation: Department of Pediatrics, Wisconsin Institutes of Medical Research, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705;
authors.forename: Willem J
authors.initials: WJ
authors.lastname: de Lange
authors.affiliation: Department of Neuroscience, Wisconsin Institutes of Medical Research, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705; Cardiovascular Research Center, Wisconsin Institutes of Medical Research, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705 garobert@wisc.edu.
authors.forename: Gail A
authors.initials: GA
authors.lastname: Robertson
mesh_terms: D002478:Cells, Cultured; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics*; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D057026:Induced Pluripotent Stem Cells / Q000166:cytology; D008564:Membrane Potentials; D032383:Myocytes, Cardiac / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics; D014176:Protein Biosynthesis; D021122:Protein Subunits; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics; D014162:Transfection
chemical_list: D051638:Ether-A-Go-Go Potassium Channels; C489622:KCNE1 protein, human; C496884:KCNH1 protein, human; D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D019837:Ryanodine Receptor Calcium Release Channel
keywords: KCNH2; cotranslational assembly; hERG; hERG 1a/1b; microtranslatome