PerspectiveVirology

Unanchored ubiquitin in virus uncoating

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Science  24 Oct 2014:
Vol. 346, Issue 6208, pp. 427-428
DOI: 10.1126/science.1261509

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Summary

Misfolded proteins in eukaryotic cells can be modified with the small protein ubiquitin (Ub). The conjugation of a chain of Ub proteins [polyubiquitin (poly-Ub)] targets a substrate for destruction by complexes called proteasomes (1). But unanchored poly-Ub chains are emerging as key factors in multiple cellular responses, including innate antiviral pathways (2, 3). Such free chains can also activate the aggresome pathway, another mechanism that degrades unwanted proteins when the proteasome system is overwhelmed or inhibited (4). On page 473 of this issue, Banerjee et al. (5) report that influenza virus engages the host cell's aggresome system by carrying unanchored poly-Ub chains. The strategy allows the virus to “uncoat” and replicate after its escape from the endosome during entry into the host cell.