Volume 6 Issue 4, April 2004

SCAR/WAVE proteins are central regulators of cell motility that coordinate actin reorganization through activation of the Arp2/3 complex. Their activity is controlled by a large complex with four other members. A new study contradicts earlier work by suggesting that the entire complex is required for SCAR/WAVE activity at the leading edge.

Protein sorting to distinct plasma membrane domains in polarized epithelial cells is thought to occur in the Golgi complex, and to be mediated in part by lipid rafts. Now, analysis of protein trafficking in live cells has revealed unexpected sorting pathways that raise new questions about the specificity and sites of action of sorting mechanisms.

Messenger RNA localization is a common way of targeting proteins to their site of function. This process is dependent on RNA signals that are interpreted by trans-acting factors. A putative RNA helicase and translational initiation factor is now shown to form a conserved complex, important for localization of oskar mRNA in Drosophila melanogaster and RNA surveillance in human cells.

The proto-oncogenic transcription factor c-Myc is a central regulator of the cell cycle and cell growth. Amino-terminal phosphorylation of c-Myc results in its proteasomal degradation. A new study shows that its dephosphorylation is regulated by the Pin1 prolyl isomerase and PP2A phosphatase, and that stabilized c-Myc can replace SV40 small T antigen in the oncogenic transformation of human cells.

The protein-only hypothesis proposes that prions propagate by imparting specific folds onto cellular proteins. This hypothesis has met with resistance, partly because of the observation that many phenotypically distinct prion 'strains' are known to exist in yeast and mammals. Recent work on yeast prions may help reconcile the occurrence of prion strains with the prion hypothesis.

New research reveals a reciprocal regulation between the CFTR chloride channel, implicated in cystic fibrosis, and several members of the SLC26 family of chloride-bicarbonate exchangers. These findings provide new insights into the mechanism of epithelial bicarbonate and fluid transport and may lead to better treatments for cystic fibrosis and congenital chloride diarrhoeas.