Fig. 3: Sequence motifs play a key role in IDR2 function.

a, IDRs from other (compare with Fig. 2e) yeast transactivators (Gal4 and Pho4) and from the GRF Reb1 conferred viability. b, Global shuffles were inviable (that is, IDR2 composition alone was insufficient for viability). c, Sequential sequence shuffling pinpointed an essential motif (EM) in the centre of IDR2. Note that LS-12 is also referred to as EM shuffle in Figs. 4c and 6. d, The EM was not conserved across orthologues or enriched for charge or hydrophobicity compared with the rest of IDR2. e, Three putative motifs are shown in the context of their IDRs. Abf1^G4 and Gal4^G4 were identified by sequence alignment of IDR2 and Gal4^768–881 (Extended Data Fig. 3g). f, Structural bioinformatics implicated the EM in forming a transient helix. g, Mutations leading to helix disruption (those encoding substitutions of glycine for other polar residues) abrogated viability. h, Schematic showing motif and context. i, Insertion of the EM into the (non-functional) FUS¹⁻¹⁶³12E (shaded blue) and Sup35 (shaded orange) contexts conferred viability. Similarly, insertion of Gal4^G4 or Abf1^G4 into FUS¹⁻¹⁶³12E conferred viability. j, Gal4^G4 rescued viability in several unrelated non-functional IDR contexts. k, IDR2 context mutations that reduced hydrophobicity but preserved the EM were inviable. l, FUS¹⁻¹⁶³12E context mutations that reduced aromaticity but preserved Gal4^G4 were inviable. m, Sub-sequences compositionally matched to Gal4^G4 and taken from a range of transcription factors also provided viability when inserted into FUS¹⁻¹⁶³12E. Con., conservation.