Tandem RNA binding sites induce self-association of the stress granule marker protein TIA-1

• Published in: Nucleic acids research Vol. 49; no. 5; pp. 2403 - 2417
• Main Authors: Loughlin, Fionna E, West, Danella L, Gunzburg, Menachem J, Waris, Saboora, Crawford, Simon A, Wilce, Matthew C J, Wilce, Jacqueline A
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 18-03-2021
• Subjects: 3' Untranslated Regions; Amyloid - ultrastructure; Binding Sites; DNA - chemistry; DNA - metabolism; Humans; Models, Molecular; NAR Breakthrough; Oligonucleotides - chemistry; Oligonucleotides - metabolism; Protein Conformation; RNA - chemistry; RNA - metabolism; T-Cell Intracellular Antigen-1 - chemistry; T-Cell Intracellular Antigen-1 - metabolism; T-Cell Intracellular Antigen-1 - ultrastructure; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Protein p53 - metabolism
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkab080

Abstract
TIA-1 is an RNA-binding protein that sequesters target RNA into stress granules under conditions of cellular stress. Promotion of stress granule formation by TIA-1 depends upon self-association of its prion-like domain that facilitates liquid-liquid phase separation and is thought to be enhanced via RNA binding. However, the mechanisms underlying the influence of RNA on TIA-1 self-association have not been previously demonstrated. Here we have investigated the self-associating properties of full-length TIA-1 in the presence of designed and native TIA-1 nucleic acid binding sites in vitro, monitoring phase separation, fibril formation and shape. We show that single stranded RNA and DNA induce liquid-liquid phase separation of TIA-1 in a multisite, sequence-specific manner and also efficiently promote formation of amyloid-like fibrils. Although RNA binding to a single site induces a small conformational change in TIA-1, this alone does not enhance phase separation of TIA-1. Tandem binding sites are required to enhance phase separation of TIA-1 and this is finely tuned by the protein:binding site stoichiometry rather than nucleic acid length. Native tandem TIA-1 binding sites within the 3′ UTR of p53 mRNA also efficiently enhance phase separation of TIA-1 and thus may potentially act as potent nucleation sites for stress granule assembly.
Graphical Abstract
Graphical Abstract
Self-association of TIA-1 is induced by tandem (specific or promiscuous) RNA binding sites in a manner that is finely tuned by the protein:RNA binding site ratio rather than RNA length.