Research Topics

Genomes and Genes


Regulation of Homeodomain Nuclear Translocation


Principal Investigator: Christopher Bonin
Abstract: DESCRIPTION (provided by applicant) Homeodomain proteins are transcription factors that regulate developmental processes through the direct activation of specific genes. The Drosophila homeodomain proteins, Extradenticle (Exd) and Homothorax (Hth), are required for proper development in Drosophila. Exd is homologous to the mammalian Pbx protein (preB cell homeobox) and Hth is homologous to the Meis (myeloid ecotropic insertion site) and Prep (Pbx regulating protein) proteins. Unlike other homeodomain proteins, Exd is localized to the cytoplasm, and hence non-functional, during the early stages of Drosophila development. At later stages of development and in specific tissues Exd is nuclear. The work outlined in this proposal is aimed at determining the mechanism of nuclear/cytoplasmic translocation of Exd. Exd contains two putative nuclear localization signals (NLS) and one putative nuclear export signal (NES). Exd also contains a domain that interacts with Hth. Binding of Hth to Exd appears to alter the availability of the putative NLS and NES sequences, effectively controlling Exd's subcellular localization. In the work to be carried out here, the putative NLSs and NES will be characterized by determining the localization of GFP proteins fused to these sequences in vivo. Proteins that co-purify with the cytoplasmic Exd will be identified by mass spectrometry and a genetic analysis of the corresponding genes will be initiated. Finally, a genetic screen will be performed to identify mutants that abrogate the cellular localization of an Exd-NES-transcription factor fusion protein. Since the misregulation of the mammalian homologs of both Exd and Hth have been implicated in cancer, determining the underlying mechanisms necessary for their regulation may be critical for understanding these diseases. We also believe that the characterization of factors required for regulating subcellular localization of Exd may lead to the identification of other proteins that rely on this process for their regulation.
Funding Period: 2002-07-01 - 2002-10-14
more information: NIH RePORT