@article {3095158,
	title = {Sequential Poly-ubiquitylation by Specialized Conjugating Enzymes Expands the Versatility of a Quality Control Ubiquitin Ligase},
	journal = {Molecular Cell},
	year = {2016},
	abstract = {<p>The Doa10 quality control ubiquitin (Ub) ligase labels proteins with uniform lysine 48-linked poly-Ub (K48-pUB) chains for proteasomal degradation. Processing of Doa10 substrates requires the activity of two Ub conjugating enzymes. Here we show that the non-canonical conjugating enzyme Ubc6 attaches single Ub molecules not only to lysines but also to hydroxylated amino acids. These Ub moieties serve as primers for subsequent poly-ubiquitylation by Ubc7. We propose that the evolutionary conserved propensity of Ubc6 to mount Ub on diverse amino acids augments the number of ubiquitylation sites within a substrate and thereby increases the target range of Doa10. Our work provides new insights on how the consecutive activity of two specialized conjugating enzymes facilitates the attachment of\&nbsp;poly-Ub to very heterogeneous client molecules. Such stepwise ubiquitylation reactions most likely represent a more general cellular phenomenon that extends the versatility yet sustains the specificity of the Ub conjugation system.</p>},
	url = {http://www.cell.com/molecular-cell/fulltext/S1097-2765(16)30373-2},
	author = {Annika Weber and Cohen, Itamar and Oliver Popp and Gunnar Dittmar and Reiss, Yuval and Thomas Sommer and Ravid, Tommer and Ernst Jarosch}
}
