Volume 10 Issue 5, May 2008

During epithelial–mesenchymal transition (EMT) cells loosen their intercellular contacts and leave the epithelial layer. Three microRNA (miRNA) families modulate EMT upstream of the key cell-adhesion protein E-cadherin, highlighting the potential importance of miRNAs in EMT-dependent processes, such as mesoderm development and tumour metastasis.

Sporadic fusion of bone-marrow-derived cells with those of developmentally unrelated structures following transplantation has previously been regarded solely as an artefact, leading to the misinterpretation that cells could 'transdifferentiate'. We now learn that heterotypic cell fusion of myelo-lymphoid cells with non-haematopoietic cells is enhanced during chronic inflammation, raising new questions about the biological significance of this controversial phenomenon.

Autophagy is a process in which cytoplasmic components are broken down to supply materials for the synthesis of essential molecules under nutrient-limiting conditions. Because this process involves random sequestration of the cytoplasm by large membrane vesicles, considerable amounts of molecules, such as ribosomes, are necessarily degraded by autophagy. However, starving cells also promote additional selective degradation of ribosomes as a requirement for survival.

SUMOylation of PML–RARα oncoprotein has been linked to its arsenic-induced degradation and the therapeutic response in acute promyelocytic leukaemia. Two groups identify PML as an in vivo target of the RING finger ubiquitin E3 ligase RNF4, which specifically binds polySUMOylated PML and is essential for the arsenic-induced catabolism of both PML and PML–RARα.

Plant stomata, which consist of paired guard cells placed on the surface of leaves, control gas exchange with the atmosphere. Anion transport by unidentified guard-cell channels closes the stomatal pore and the first component for this channel function has now been found.