The vast majority of human cancers have abnormal numbers of chromosomes, known as aneuploidy. However, the molecular basis of aneuploidy and its role in tumor development remain poorly understood. Recent studies led to the identification of a new class of mitotic regulators consisting of proteins that mediate nucleocytoplasmic transport in interphase. Our broad long-term goal is to provide insight into the biological relevance of these nuclear transport factors and their possible role in preventing chromosomal instability and tumorigenesis. The specific goal of the current proposal is to dissect the mitotic functions of the nuclear pore complex protein RanBP2 at the molecular, cellular and organismal levels, and to determine how RanBP2 downregulation promotes tumorigenesis. We have generated a series of mice in which the nucleoporin RanBP2 protein is reduced in a graded fashion from normal to zero by the use of wild-type, knockout and hypomorphic alleles. Mice lacking RanBP2 are embryonically lethal, but mice with very low amounts of the protein are viable and overtly normal. Consistent with a role for RanBP2 in mitosis, we find that these mice develop severe aneuploidy. The main mitotic defect that we observe is chromatin-bridge formation in anaphase, a phenotype reminiscent of impaired topoisomerase II? function.
In specific aim one, we will use both genetic and biochemical approaches to establish the mechanism by which RanBP2 regulates accurate sister chromatid segregation in anaphase. Furthermore, using conditional knockout cells we will determine the critical functional domain(s) of RanBP2. Preliminary studies show that mice with low levels of RanBP2 have increased susceptibility to spontaneous and carcinogen-induced tumors, especially lung tumors. Importantly, using quantitative RT-PCR analysis of primary human tumors and human cancer cell lines we found that RanBP2 expression is dramatically reduced in many lung adenocarcinomas, suggesting that RanBP2 has a tumor suppressive function in both mice and humans.
In specific aim two, we will use already established and newly designed RanBP2 mutant mouse models to resolve the mechanism by which RanBP2 insufficiency promotes tumorigenesis. The profound sensitivity of RanBP2 mutant mice to the carcinogen DMBA indicates that RanBP2 insufficiency strongly synergizes with other gene mutations in tumorigenesis.
In specific aim three, we will identify these cancer gene mutations by the use of the """"""""Sleeping Beauty"""""""" transposon system. In addition to this unbiased approach, we will use a candidate gene approach to determine whether K-ras synergizes with RanBP2 deficiency in lung carcinogenesis. At the basic research level, completion of these aims will provide insight into the mechanism by which a prominent nuclear transport factor maintains chromosomal stability and prevents cancer. At the clinical level, these studies may provide the basis for improved detection, prevention and treatment of cancer in humans.
|Meehan, Anne M; Saenz, Dyana T; Guevera, Rebekah et al. (2014) A cyclophilin homology domain-independent role for Nup358 in HIV-1 infection. PLoS Pathog 10:e1003969|
|Hamada, Masakazu; Malureanu, Liviu A; Wijshake, Tobias et al. (2012) Reprogramming to pluripotency can conceal somatic cell chromosomal instability. PLoS Genet 8:e1002913|
|Hamada, Masakazu; Haeger, Anna; Jeganathan, Karthik B et al. (2011) Ran-dependent docking of importin-beta to RanBP2/Nup358 filaments is essential for protein import and cell viability. J Cell Biol 194:597-612|
|Ricke, Robin M; van Deursen, Jan M (2011) Correction of microtubule-kinetochore attachment errors: mechanisms and role in tumor suppression. Semin Cell Dev Biol 22:559-65|
|Hussain, S; Foreman, O; Perkins, S L et al. (2010) The de-ubiquitinase UCH-L1 is an oncogene that drives the development of lymphoma in vivo by deregulating PHLPP1 and Akt signaling. Leukemia 24:1641-55|
|Dawlaty, Meelad M; Malureanu, Liviu; Jeganathan, Karthik B et al. (2008) Resolution of sister centromeres requires RanBP2-mediated SUMOylation of topoisomerase IIalpha. Cell 133:103-15|
|Ricke, Robin M; van Ree, Janine H; van Deursen, Jan M (2008) Whole chromosome instability and cancer: a complex relationship. Trends Genet 24:457-66|
|Satterly, Neal; Tsai, Pei-Ling; van Deursen, Jan et al. (2007) Influenza virus targets the mRNA export machinery and the nuclear pore complex. Proc Natl Acad Sci U S A 104:1853-8|
|Jeganathan, Karthik B; Baker, Darren J; van Deursen, Jan M (2006) Securin associates with APCCdh1 in prometaphase but its destruction is delayed by Rae1 and Nup98 until the metaphase/anaphase transition. Cell Cycle 5:366-70|
|Baker, Darren J; Jeganathan, Karthik B; Malureanu, Liviu et al. (2006) Early aging-associated phenotypes in Bub3/Rae1 haploinsufficient mice. J Cell Biol 172:529-40|
Showing the most recent 10 out of 17 publications