This proposal describes a five-year mentored research and training plan for the development of the principal investigator's career as a physician scientist. His immediate goal is to discover molecular targets for anti-fibrotic therapy, with a long-term goal of transitioning to a career as an independent investigator. This research and training will be carried out in the Department of Medicine at the University of Minnesota, an institution committed to developing physician scientists, ensuring that trainees have access to the resources, faculty and other support necessary for such development. The Principal Investigator's career development plan consists of research, coursework and seminars to present his research findings and ideas, and receive feedback from established investigators. He has assembled a multidisciplinary advisory committee to guide his development as a scientist. In fibro-proliferative disorders such as idiopathic pulmonary fibrosis (IPF) as well as in cancer, persistent cells demonstrate aberrant cell proliferation and dysregulated apoptosis as well as pathological activation of cap-dependent translation. Evidence suggests that increased cap-dependent translation suppresses apoptosis by selectively activating the translation of specific mRNAs encoding rescue proteins. In cap-dependent translation, binding of the translation initiation complex to the to the 5' cap of the mRNA is the rate-limiting step, dependent on the molecule elF4E, which directly binds to the cap and to elF4G, a docking protein connecting elF4E and the ribosomal translation complex. In IRES mediated translation, mRNA is recruited directly to elF4G, bypassing elF4E. Suppression of cap-dependent translation by the repressor protein 4EBP1 sensitizes malignant ceils to apoptosis, however, apoptosis increases until a certain threshold of cap-dependent translational suppression is reached, after which the level of IRES-mediated translation increases and apoptosis decreases. We hypothesize two possible mechanisms for this effect: 1.) rescue proteins are produced via IRES mediated translation; 2.) translation of cap-dependent pro-apoptotic proteins is suppressed.
In specific aim 1 we propose to discriminate between these two possibilities by creating cell lines stably overexpressing elF4G wild type and mutant elF4G lacking the elF4E binding site. This will allow us to selectively increase IRES mediated translation without significantly altering cap-dependent translation, elucidating the relationship between IRES-mediated translation and apoptosis.
In specific aim 2 we propose to identify the transcripts mediating the antiapoptotic function of elF4E, by combining polyribosome and microarray analysis to pinpoint mRNAs that become translationally active under proapoptotic conditions when cells are rescued from apoptosis by elF4E. Our studies are designed to provide information that is critical to moving forward with therapeutics targeting translational control of apoptosis.
| Larsson, Ola; Perlman, David M; Fan, Danhua et al. (2006) Apoptosis resistance downstream of eIF4E: posttranscriptional activation of an anti-apoptotic transcript carrying a consensus hairpin structure. Nucleic Acids Res 34:4375-86 |
