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The study of cancer cells in culture have led to the description of the "transformed phenotype" which alludes, in part, to the alterations in serum and adhesion dependent growth properties of cells. Furthermore, in malignant transformation there are changes in cell morphology, loss of contact inhibition and adherens junctions and increased cell migration. A vast majority of these changes have been attributed to alterations in the actin cytoskeleton. The small GTPases, Rho, Rac and CDC42, are believed to be responsible for the formation of actin mediated assemblies such as stress fibers, focal adhesions, lamellipodia and filipodia, while Rap1 is implicated in adherens junctions in both normal and transformed cells. However, the mechanism(s) responsible for loss of control of the small GTPases in cancer, however, is not clear. The primary reason is that many individual proteins in the large complex of proteins around actin mediated cytoskeletal structures still remain unidentified. The detailed description of these cytoskeletal protein networks will come by combining the power of genetics with proteomics, and will provide further insight into cancer progression and distant metastasis. This is the focus my laboratory investigation.


  • An Isoform of GTPase Regulator DOCK4 Localizes to the Stereocilia in the Inner Ear and Binds to Harmonin (USH1C). Yan D, Li F, Hall ML, Sage C, Hu WH, Giallourakis C, Upadhyay G, Ouyang XM, Du LL, Bethea JR, Chen ZY, Yajnik V, Liu XZ. J Mol Biol. 2006 Jan 23; [Epub ahead of print]
  • DOCK4, a GTPase activator, is disrupted during tumorigenesis. Yajnik V, Paulding C, Sordella R, McClatchey AI, Saito M, Wahrer DC, Reynolds P, Bell DW, Lake R, van den Heuvel S, Settleman J, Haber DA. Cell. 2003 Mar 7;112(5):673-84.
  • Cloning and mutational analysis of the Shc-phosphotyrosine interaction/ phosphotyrosine-binding domain. Yajnik V, Blaikie P, Margolis B. Methods Mol Biol. 1998;84:223-35.
  • Yajnik, P. Blaikie, P. Bork, B. Margolis (1996) Identification of residues within the Shc PTB/PI domain crucial for phosphopeptide interaction. J. Biol. Chem 271: 1813-1816.
  • Isakoff, Y. Yu, Y. Su, P. Blaikie, V. Yajnik, K. Weidner, M. Sachs, B. Margolis and E. Skolnik (1996) The Shc PTB/PI domain is required for Shc tyrosine phosphorylation by the insulin receptor (IR) and recognizes an NPXY motif on the IR that is distinct from IRS-1 in vivo. J. Biol. Chem. 271: 2410-2416.
  • Ooi, V. Yajnik, D. Immanuel, M. Gordon, J.J. Moskow, A.M. Buchberg, and B. Margolis (1995) The cloning of Grb 10 reveals a new family of SH2 domain proteins. Oncogene 10: 1621-1630.