Dlg (Discs large), Scrib (Scribble) and Lgl (Lethal giant larvae) are evolutionarily conserved components of a common genetic pathway that link the seemingly disparate functions of cell polarity and cell proliferation in epithelial cells. dlg, scrib and lgl have been identified as tumour suppressor genes in Drosophila, mutations of which cause similar phenotypes, involving disruption of cell polarity and neoplastic overgrowth of tissues. The molecular mechanisms by which Dlg, Scrib and Lgl proteins regulate cell proliferation are not (...) clear, but there is some evidence that epithelial polarisation is required for this regulation. Dlg, Scrib and Lgl are highly conserved between human and Drosophila, and we discuss evidence that these proteins also play a role in cancer progression in humans. BioEssays 25:542–553, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

RAS GTPases play essential roles in normal development and are direct drivers of human cancers. Three decades of study have failed to wholly characterize pathways stimulated by activated RAS, driven by engagement with ‘effector’ proteins that have RAS binding domains (RBDs). Bone fide effectors must bind directly to RAS GTPases in a nucleotide‐dependent manner, and this interaction must impart a clear change in effector activity. Despite this, for most proteins currently deemed effectors there is little mechanistic understanding of how binding (...) to the GTPase alters protein function. There has also been limited effort to comprehensively resolve the specificity of effector binding to the full array of RAS superfamily GTPase proteins. This review will summarize what is known about RAS‐driven activation for an array of potential effector proteins, focusing on structural and mechanistic effects and highlighting how little is still known regarding this key paradigm of cellular signal transduction. (shrink)