TCL/RhoJ Plasma Membrane Localization and Nucleotide Exchange Is Coordinately Regulated by Amino Acids within the N Terminus and a Distal Loop Region.

TCL/RhoJ is a Cdc42-related Rho GTPase with reported activities in endothelial cell biology and angiogenesis, metastatic melanoma, and corneal epithelial cells; however, less is known about how it is inherently regulated in comparison to its closest homologues TC10 and Cdc42. TCL has an N-terminal extension of 18 amino acids in comparison to Cdc42, but the function of this amino acid sequence has not been elucidated. A truncation mutant lacking the N terminus (ΔN) was found to alter TCL plasma membrane localization and nucleotide binding, and additional truncation and point mutants mapped the alterations of TCL biochemistry to amino acids 17-20. Interestingly, whereas the TCL ΔN mutant clearly influenced nucleotide exchange, deletion of the N terminus from its closest homologue, TC10, did not have a similar effect. Chimeras of TCL and TC10 revealed amino acids 121-129 of TCL contributed to the differences in nucleotide loading. Together, these results identify amino acids within the N terminus and a loop region distal to the nucleotide binding pocket of TCL capable of allosterically regulating nucleotide exchange and thus influence membrane association of the protein.

Nuclear Dynamics and Chromatin Structure: Implications for Pancreatic Cancer.

Changes in nuclear shape have been extensively associated with the dynamics and functionality of cancer cells. In most normal cells, nuclei have a regular ellipsoid shape and minimal variation in nuclear size; however, an irregular nuclear contour and abnormal nuclear size is often observed in cancer, including pancreatic cancer. Furthermore, alterations in nuclear morphology have become the 'gold standard' for tumor staging and grading. Beyond the utility of altered nuclear morphology as a diagnostic tool in cancer, the implications of altered nuclear structure for the biology and behavior of cancer cells are profound as changes in nuclear morphology could impact cellular responses to physical strain, adaptation during migration, chromatin organization, and gene expression. Here, we aim to highlight and discuss the factors that regulate nuclear dynamics and their implications for pancreatic cancer biology.