Publications & Reports

Novel properties of the protein kinase CK2-site-regulated nuclear- localization sequence of the interferon-induced nuclear factor IFI 16.

Briggs LJ, Johnstone RW, Elliot RM, Xiao CY, Dawson M, Trapani JA, Jans DA
Nuclear Signalling Laboratory, Division for Biochemistry and Molecular Biology, John Curtin School of Medical Research, Australian National University, P.O. Box 334, Canberra City, A.C.T. 2601, Australia.


Members of the interferon-induced class of nuclear factors possess a putative CcN motif, comparable with that within proteins such as the simian virus 40 large tumour antigen (T-ag), which confers phosphorylation-mediated regulation of nuclear-localization sequence (NLS)-dependent nuclear import. Here we examine the functionality of the interferon-induced factor 16 (IFI 16) CcN motif, demonstrating its ability to target a heterologous protein to the nucleus, and to be phosphorylated specifically by the CcN-motif-phosphorylating protein kinase CK2 (CK2). The IFI 16 NLS, however, has novel properties, conferring ATP-dependent nuclear import completely independent of cytosolic factors, as well as binding to nuclear components. The IFI 16 NLS is not recognized with high affinity by the NLS-binding importin heterodimer, and transport mediated by it is insensitive to non-hydrolysable GTP analogues. The IFI 16 NLS thus mediates nuclear import through a pathway completely distinct from that of conventional NLSs, such as that of T-ag, but intriguingly resembling that of the NLS of the HIV-1 transactivator protein Tat. Since the IFI 16 CK2 site enhances nuclear import through facilitating binding to nuclear components, this represents a novel mechanism by which the site regulates nuclear-protein import, and constitutes a difference between the IFI 16 and Tat NLSs that may be of importance in the immune response.


  • Journal: The Biochemical Journal
  • Published: 01/01/2001
  • Volume: 353
  • Issue: Pt 1
  • Pagination: 69-77