Cell signalling

Spred is a Sprouty-related suppressor of Ras signalling. Wakioka, T. et al. Nature 412, 647?651 (2001) [PubMed]

Wakioka and colleagues describe the cloning and characterization of two receptor tyrosine kinase substrates, Spred-1 and 2, which contain an amino-terminal Ena/vasodilator-stimulated phosphoprotein homology-1 domain and a carboxy-terminal Sprouty-related domain. Like Sprouty ? which inhibits epidermal- and fibroblast-growth-factor-mediated signalling ? Spred suppresses the mitogen-activated protein kinase (MAPK) pathway. It does this by associating with Ras, thereby somehow suppressing the phosphorylation and activation of Raf.

Development

Barentsz is essential for the posterior localization of oskar mRNA and co-localizes with it to the posterior pole. Van Eeden, F. J. M. et al. J. Cell Biol. 154, 511?523 (2001) [PubMed]

During embryonic development, the localized translational activation of oskar messenger RNA at the posterior pole of the Drosophila oocyte defines where the abdomen and germ cells form. This localization is thought to involve active transport along the cytoskeleton, but how the mRNA is coupled to this process remains unknown. Van Eeden and colleagues report the phenotypic and molecular characterization of a novel locus called barentsz, which co-localizes with oskar mRNA and is specifically required for the movement of oskar mRNA from the anterior to the posterior of the oocyte. This suggests that Barentsz is essential for the posterior localization of oskar mRNA and behaves as a specific component of the oskar RNA transportation process.

Translation

The path of messenger RNA through the ribosome Yusupova, G. Z., Yusupov, M. M., Cate J. H. D. & Noller H. F. Cell 106, 233?241 (2001) [PubMed]

The ribosome translates messenger RNA (mRNA) into proteins but the molecular mechanisms that influence the unwinding of the mRNA secondary structure and correct reading of the message have remained unknown. Yusupova and colleagues have identified these processes by mapping the complete path of the mRNA through the 70S ribosome of Thermus thermophilus using X-ray crystallography. They report that the mRNA is threaded through a channel that wraps around the neck of the 30S subunit and that the locations of downstream regions of the mRNA in the ribosome have implications for translational initiation, frame shifting and other functional interactions. The authors predict that mRNAs will follow similar paths in eukaryotic ribosomes and hope their findings will provide a basis for designing strategies to test emerging models for the molecular basis of ribosomal dynamics.