These authors contributed equally to this work.
Nap1 and Chz1 have Separate Htz1 Nuclear Import and Assembly Functions
Article first published online: 19 NOV 2009
© 2009 John Wiley & Sons A/S
Volume 11, Issue 2, pages 185–197, February 2010
How to Cite
Straube, K., Blackwell, J. S. and Pemberton, L. F. (2010), Nap1 and Chz1 have Separate Htz1 Nuclear Import and Assembly Functions. Traffic, 11: 185–197. doi: 10.1111/j.1600-0854.2009.001010.x
- Issue published online: 4 JAN 2010
- Article first published online: 19 NOV 2009
- Received 28 July 2009, revised and accepted for publication 28 October 2009, uncorrected manuscript published online 30 October 2009, published online 19 November 2009
- Sacharromyces cerevisiae;
- histone chaperone;
- nuclear import
We analyzed the nuclear import and regulation of the yeast histone variant Htz1 (H2A.Z), and the role of histone chaperones Nap1 and Chz1 in this process. Copurification suggested that Htz1 and H2B dimerized in the cytoplasm prior to import. Like H2B, Htz1 contained a nuclear localization signal (NLS) in its N-terminus that is recognized by multiple karyopherins (also called importins), indicating multiple transport pathways into the nucleus. However, Kap114 and Kap123 appeared to play the major role in Htz1 import. We also identified a role for Nap1 in the import of Htz1/H2B heterodimers, and Nap1 formed a RanGTP-insensitive import complex with Htz1/H2B and Kap114. Nap1 was necessary for maintaining a soluble pool of Htz1, indicating that its chaperone function may be important for the dynamic exchange of histones within nucleosomes. In contrast, Chz1 was imported by a distinct import pathway, and Chz1 did not appear to interact with Htz1 in the cytoplasm. Genetic analysis indicated that NAP1 has a function in the absence of HTZ1 that is not shared with CHZ1. This provides further evidence that the histone chaperones Nap1 and Chz1 have separate Htz1-dependent and -independent functions.