We are grateful to Lubor Borsig, Daniel Rhyner, Carole Oertli, Jürg Cabalzar, Christoph Rutschmann, and Charlotte Burger for technical assistance. We are grateful to the Functional Genomics Center Zurich for its support with mass spectrometric analysis.
This work was supported by a Swiss National Science Foundation Grant 310030-129633 to T.H.