title: Hyperphosphorylation amplifies UPF1 activity to resolve stalls in nonsense-mediated mRNA decay.
abstract: Many gene expression factors contain repetitive phosphorylation sites for single kinases, but the functional significance is poorly understood. Here we present evidence for hyperphosphorylation as a mechanism allowing UPF1, the central factor in nonsense-mediated decay (NMD), to increasingly attract downstream machinery with time of residence on target mRNAs. Indeed, slowing NMD by inhibiting late-acting factors triggers UPF1 hyperphosphorylation, which in turn enhances affinity for factors linking UPF1 to decay machinery. Mutational analyses reveal multiple phosphorylation sites contributing to different extents to UPF1 activity with no single site being essential. Moreover, the ability of UPF1 to undergo hyperphosphorylation becomes increasingly important for NMD when downstream factors are depleted. This hyperphosphorylation-dependent feedback mechanism may serve as a molecular clock ensuring timely degradation of target mRNAs while preventing degradation of non-targets, which, given the prevalence of repetitive phosphorylation among central gene regulatory factors, may represent an important general principle in gene expression.
authors: Division of Biological Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors: Sébastien
authors: S
authors: Durand
authors: Division of Biological Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors: Tobias M
authors: TM
authors: Franks
authors: Division of Biological Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors: Jens
authors: J
authors: Lykke-Andersen
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D004252:DNA Mutational Analysis; D015180:Electrophoresis, Gel, Two-Dimensional; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D059365:Nonsense Mediated mRNA Decay; D010766:Phosphorylation; D000067996:RAW 264.7 Cells; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; C484446:Rent1 protein, mouse; D015534:Trans-Activators; D000255:Adenosine Triphosphate; D020365:RNA Helicases; C101828:UPF1 protein, human