Doing Triple Duty

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Science  12 Dec 2003:
Vol. 302, Issue 5652, pp. 1863-1865
DOI: 10.1126/science.302.5652.1863d

Adenovirus is a small DNA virus that replicates its genome and assembles new virus particles inside the nucleus of the host cell. The protein components of the viral capsid are synthesized in the cytosol and so must be imported into the nucleus. Wodrich et al. show that one of the viral capsid proteins, protein VI, has near its C terminus both nuclear localization and export signals (NLS and NES). Because protein VI binds to the major adenovirus capsid protein (hexon) in the cytosol, it can carry hexon molecules into the nucleus, using its NLS to hitch a ride on the host nuclear importers, and then return empty-handed to the cytosol via its NES-exporter interaction. When capsid proteins are sufficiently concentrated in the nucleus to allow for efficient virus assembly, both nuclear transport signals in protein VI are degraded by proteolysis, trapping the protein in the nucleus and uncovering its third function as a structural component of the capsid itself. — SMH

EMBO J. 22, 6245 (2003).

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