Proteins bearing a classical nuclear localization signal (cNLS) are imported into the nucleus of eukaryotic cells by the heterodimer importin a/b (also known as karyopherin a/b). This import pathway, often referred as classical, also requires the small GTPase Ran, which exists mainly bound to GTP in the nucleoplasm and to GDP in the cytoplasm. RanGTP allows movement of the import complex through the Nuclear Pore Complex, by releasing importin b from high affinity binding sites as well as releasing the import cargo into the nucleoplasm. In the past ten years a wealth of cellular, biochemical, and structural data has dramatically increased our understanding of nuclear transport. It has become evident that, in addition to the classical importin a/b- dependent nuclear import pathway, eukaryotic cells have developed a remarkable variety of alternative import pathways. Whereas we do not fully understand the need of such transport """"""""redundancy"""""""", alternative import pathways often rely on distinct non-classical transport signals, and use diverse mechanisms of import. In this proposal we intend to investigate the molecular basis for the recognition and nuclear import of three non-classical cargos, which include the adaptor snurportin, HIV-1 Rev protein, and the transcription factor STAT1. Our research is aimed at understanding how non-classical NLSs are recognized by importin a and b and how their nuclear import is regulated, both in terms of energy requirement and kinetic of accumulation in the nucleus.
Specific Aims of our work include: 1. Determining the molecular basis for the Ran and energy independent nuclear import of snurportin 2. Carry out a quantitative structural and functional analysis of HIV-1 Rev-NLS 3. Define the molecular basis for the recognition of STAT1 """"""""dinner-specific""""""""NLS by importin a-5.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Nuclear Dynamics and Transport (NDT)
Program Officer
Flicker, Paula F
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Thomas Jefferson University
Schools of Medicine
United States
Zip Code
Sankhala, Rajeshwer S; Lokareddy, Ravi K; Begum, Salma et al. (2017) Three-dimensional context rather than NLS amino acid sequence determines importin ? subtype specificity for RCC1. Nat Commun 8:979
Kralt, Annemarie; Jagalur, Noorjahan B; van den Boom, Vincent et al. (2015) Conservation of inner nuclear membrane targeting sequences in mammalian Pom121 and yeast Heh2 membrane proteins. Mol Biol Cell 26:3301-12
Pumroy, Ruth A; Ke, Song; Hart, Darren J et al. (2015) Molecular determinants for nuclear import of influenza A PB2 by importin ? isoforms 3 and 7. Structure 23:374-84
Lokareddy, Ravi K; Hapsari, Rizqiya A; van Rheenen, Mathilde et al. (2015) Distinctive Properties of the Nuclear Localization Signals of Inner Nuclear Membrane Proteins Heh1 and Heh2. Structure 23:1305-1316
Pumroy, Ruth A; Cingolani, Gino (2015) Diversification of importin-? isoforms in cellular trafficking and disease states. Biochem J 466:13-28
Pumroy, Ruth Anne; Cingolani, Gino (2014) Jamming up the ""?-staple"": regulation of SIRT1 activity by its C-terminal regulatory segment (CTR). J Mol Biol 426:507-9
Lokareddy, Ravi Kumar; Bhardwaj, Anshul; Cingolani, Gino (2013) Atomic structure of dual-specificity phosphatase 26, a novel p53 phosphatase. Biochemistry 52:938-48
Pumroy, Ruth A; Nardozzi, Jonathan D; Hart, Darren J et al. (2012) Nucleoporin Nup50 stabilizes closed conformation of armadillo repeat 10 in importin ?5. J Biol Chem 287:2022-31
Lott, Kaylen; Bhardwaj, Anshul; Sims, Peter J et al. (2011) A minimal nuclear localization signal (NLS) in human phospholipid scramblase 4 that binds only the minor NLS-binding site of importin alpha1. J Biol Chem 286:28160-9
Koksal, Adem C; Cingolani, Gino (2011) Dimerization of Vaccinia virus VH1 is essential for dephosphorylation of STAT1 at tyrosine 701. J Biol Chem 286:14373-82

Showing the most recent 10 out of 17 publications