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Nature Cell Biology 3, 1086–1091 (1 December 2001) | doi:10.1038/ncb1201-1086

Distinct AAA-ATPase p97 complexes function in discrete steps of nuclear assembly

Martin Hetzer , Hemmo H. Meyer , Tobias C. Walther , Daniel Bilbao-Cortes , Graham Warren & Iain W. Mattaj

Although nuclear envelope (NE) assembly is known to require the GTPase Ran, the membrane fusion machinery involved is uncharacterized. NE assembly involves formation of a reticular network on chromatin, fusion of this network into a closed NE and subsequent expansion. Here we show that p97, an AAA-ATPase previously implicated in fusion of Golgi and transitional endoplasmic reticulum (ER) membranes together with the adaptor p47, has two discrete functions in NE assembly. Formation of a closed NE requires the p97–Ufd1–Npl4 complex, not previously implicated in membrane fusion. Subsequent NE growth involves a p97–p47 complex. This study provides the first insights into the molecular mechanisms and specificity of fusion events involved in NE formation.