Cell division

Dynamic localization of a cytoplasmic signal transduction response regulator controls morphogenesis during the Caulobacter cell cycle. Jacobs, C. et al. Proc. Natl Acad. Sci. USA 98 , 4095?4100 (2001) [PubMed]

The bacterium Caulobacter crescentus divides asymmetrically to generate a small 'swarmer' cell and a larger 'stalked' cell. This asymmetry, it turns out, is generated and maintained by dynamic changes in the subcellular localization of components involved in a signal-transduction cascade. Whereas the DivK response regulator protein is found throughout the cytoplasm of the swarmer cell, it is localized to the pole of the stalked cell. And these localization patterns are controlled by the membrane-bound DivJ and PleC histidine kinases, which themselves are asymmetrically localized at opposite poles of the dividing cell.

Signal transduction

p53 induction of heparin-binding EGF-like growth factor counteracts p53 growth suppression through activation of MAPK and PI3K/Akt signalling cascades. Fang, L. et al. EMBO J. 20 , 1931?1939 (2001) [PubMed]

Transcriptional targets of p53 abound, and this paper reports the identification of a new one ? the heparin-binding epithelial-growth-factor-like growth factor. Its expression is induced in response to DNA damage, in a p53-dependent way, and it in turn activates the mitogen-activated protein kinase and phosphatidyl-inositol 3-kinase/Akt pathways to promote cell survival.

Development

Steroid regulation of autophagic programmed cell death during development. Lee, C.-Y. & Baehrecke, E. H. Development 128 , 1443?1455 (2001) [PubMed]

Steroid hormones activate programmed cell death during development to remove cells that are not needed. This study of Drosophila larval salivary glands reveals that developmental death involves genes involved in apoptosis ? including caspases ? yet the dying cells have morphological characteristics typical of autophagic cell death. These results indicate that there could be common regulatory mechanisms between the distinct processes of apoptosis and autophagy.

Ribosomes

Crystal structure of the ribosome at 5.5 Å resolution. Yusupov, M. M. et al. Science March 29 2001 (epub ahead of print) [PubMed]

Harry Noller and colleagues report the crystal structure of the complete Thermus thermophilus 70S ribosome, complete with bound messenger and transfer RNAs, at a resolution of 5.5 Å. All of the ribosomal chains (16S, 23S and 5S) and most of the ribosomal proteins can be fitted to the electron-density map, and with this level of detail it is possible to formulate ? and test ? models for the mechanism of translation.