Baur, Tina; Ramadan, Kristijan; Schlundt, Andreas; Kartenbeck, Jürgen; Meyer, Hemmo:

NSF- and SNARE-mediated membrane fusion is required for nuclear envelope formation and completion of nuclear pore complex assembly in Xenopus laevis egg extracts

In: Journal of Cell Science, Jg. 120 (2007) ; Nr. 16, S. 2895-2903
ISSN: 0021-9533
Zeitschriftenaufsatz / Fach: Biologie
Fakultät für Biologie » Chemische Biologie
Abstract:
Despite the progress in understanding nuclear envelope (NE) reformation
   after mitosis, it has remained unclear what drives the required membrane
   fusion and how exactly this is coordinated with nuclear pore complex
   (NPC) assembly. Here, we show that, like other intracellular fusion
   reactions, NE fusion in Xenopus laevis egg extracts is mediated by SNARE
   proteins that require activation by NSF. Antibodies against Xenopus NSF,
   depletion of NSF or the dominant-negative NSFE329Q variant specifically
   inhibited NE formation. Staging experiments further revealed that NSF
   was required until sealing of the envelope was completed. Moreover,
   excess exogenous alpha-SNAP that blocks SNARE function prevented
   membrane fusion and caused accumulation of non-flattened vesicles on the
   chromatin surface. Under these conditions, the nucleoporins Nup107 and
   gp210 were fully recruited, whereas assembly of FxFG-repeat-containing
   nucleoporins was blocked. Together, we define NSF- and SNARE-mediated
   membrane fusion events as essential steps during NE formation downstream
   of Nup107 recruitment, and upstream of membrane flattening and
   completion of NPC assembly.