title: Together, Rpn10 and Dsk2 can serve as a polyubiquitin chain-length sensor.
abstract: As a signal for substrate targeting, polyubiquitin meets various layers of receptors upstream to the 26S proteasome. We obtained structural information on two receptors, Rpn10 and Dsk2, alone and in complex with (poly)ubiquitin or with each other. A hierarchy of affinities emerges with Dsk2 binding monoubiquitin tighter than Rpn10 does, whereas Rpn10 prefers the ubiquitin-like domain of Dsk2 to monoubiquitin, with increasing affinities for longer polyubiquitin chains. We demonstrated the formation of ternary complexes of both receptors simultaneously with (poly)ubiquitin and found that, depending on the ubiquitin chain length, the orientation of the resulting complex is entirely different, providing for alternate signals. Dynamic rearrangement provides a chain-length sensor, possibly explaining how accessibility of Dsk2 to the proteasome is limited unless it carries a properly tagged cargo. We propose a mechanism for a malleable ubiquitin signal that depends both on chain length and combination of receptors to produce tetraubiquitin as an efficient signal threshold.
authors.affiliation: Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Organization, University of Maryland, College Park, 20910, USA.
authors.forename: Daoning
authors.initials: D
authors.lastname: Zhang
authors.forename: Tony
authors.initials: T
authors.lastname: Chen
authors.forename: Inbal
authors.initials: I
authors.lastname: Ziv
authors.forename: Rina
authors.initials: R
authors.lastname: Rosenzweig
authors.forename: Yulia
authors.initials: Y
authors.lastname: Matiuhin
authors.forename: Vered
authors.initials: V
authors.lastname: Bronner
authors.forename: Michael H
authors.initials: MH
authors.lastname: Glickman
authors.forename: David
authors.initials: D
authors.lastname: Fushman
mesh_terms: D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D025821:Polyubiquitin / Q000737:chemistry / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014452:Ubiquitins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; C100415:DSK2 protein, S cerevisiae; C122019:RPN10 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; D025821:Polyubiquitin; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease