title: Catalytic and chaperone-like functions in an intrinsically disordered protein associated with desiccation tolerance.
abstract: Intrinsically disordered proteins (IDPs) lack well-defined structure but are widely represented in eukaryotic proteomes. Although the functions of most IDPs are not understood, some have been shown to have molecular recognition and/or regulatory roles where their disordered nature might be advantageous. Anhydrin is an uncharacterized IDP induced by dehydration in an anhydrobiotic nematode, Aphelenchus avenae. We show here that anhydrin is a moonlighting protein with two novel, independent functions relating to desiccation tolerance. First, it has a chaperone-like activity that can reduce desiccation-induced enzyme aggregation and inactivation in vitro. When expressed in a human cell line, anhydrin localizes to the nucleus and reduces the propensity of a polyalanine expansion protein associated with oculopharyngeal muscular dystrophy to form aggregates. This in vivo activity is distinguished by a loose association of anhydrin with its client protein, consistent with a role as a molecular shield. In addition, anhydrin exhibits a second function as an endonuclease whose substrates include supercoiled, linear, and chromatin linker DNA. This nuclease activity could be involved in either repair of desiccation-induced DNA damage incurred during anhydrobiosis or in apoptotic or necrotic processes, for example, but it is particularly unexpected for anhydrin because IDP functions defined to date anticorrelate with enzyme activity. Enzymes usually require precise three-dimensional positioning of residues at the active site, but our results suggest this need not be the case. Anhydrin therefore extends the range of IDP functional categories to include catalysis and highlights the potential for the discovery of new functions in disordered proteomes.
authors.affiliation: Department of Chemical Engineering and Biotechnology, Institute of Biotechnology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QT, United Kingdom.
authors.forename: Sohini
authors.initials: S
authors.lastname: Chakrabortee
authors.forename: Filip
authors.initials: F
authors.lastname: Meersman
authors.forename: Gabriele S
authors.initials: GS
authors.lastname: Kaminski Schierle
authors.forename: Carlos W
authors.initials: CW
authors.lastname: Bertoncini
authors.forename: Brian
authors.initials: B
authors.lastname: McGee
authors.forename: Clemens F
authors.initials: CF
authors.lastname: Kaminski
authors.forename: Alan
authors.initials: A
authors.lastname: Tunnacliffe
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D055162:Biocatalysis; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D003890:Desiccation; D006801:Humans; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D017187:Tylenchida / Q000737:chemistry* / Q000378:metabolism
chemical_list: D018832:Molecular Chaperones; D004247:DNA
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