TY - JOUR T1 - Together, Rpn10 and Dsk2 Can Serve as a Polyubiquitin Chain-Length Sensor JF - Molecular Cell Y1 - 2009 A1 - Zhang,Daoning A1 - Chen,Tony A1 - Ziv,Inbal A1 - Rosenzweig,Rina A1 - Matiuhin,Yulia A1 - Bronner,Vered A1 - Glickman,Michael H. A1 - Fushman, David KW - Proteins KW - signaling AB - SummaryAs 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. VL - 36 SN - 1097-2765 UR - http://www.sciencedirect.com/science/article/pii/S1097276509008260 CP - 6 M3 - 10.1016/j.molcel.2009.11.012 ER -