P53

C. elegans p53: Role in apoptosis, meiosis and stress resistance.

Derry, W. B., Putzke, A. P. & Rothman, J. H. Science 13 September (2001) (epub ahead of print) [Contents page]

Previous searches of the Caenorhabditis elegans genome had indicated that this organism does not have a p53-like gene. Now, however, using additional algorithms, Derry et al. have identified a p53 homologue called cep-1, which is expressed in embryos. It promotes DNA-damage induced apoptosis, and is required for meiotic chromosome segregation in the germ line.

Development

Argosomes: a potential vehicle for the spread of morphogens through epithelia.

Greco, V., Hannus, M. & Eaton, S. Cell 106, 633?645 (2001) [PubMed]

Pattern formation in developing tissues occurs in response to morphogen gradients. But some morphogens are tightly associated with the plasma membrane, and Greco et al. now describe how these proteins might be distributed through the epithelium in Drosophila imaginal discs. They propose the existence of membrane exovesicles ? called argosomes ? which travel through adjacent tissue, acting as a vehicle for the spread of morphogens, such as Wingless.

RNA splicing

Crystal structure of the human nuclear cap binding complex.

Mazza, C. et al. Mol. Cell 8, 383?396 (2001) [PubMed]

The nuclear cap binding complex binds the 5′ cap of nascent RNA transcripts, and is involved in pre-messenger RNA splicing. The authors show that the CBP80 subunit contains three helical domains. The first is an MIF4G domain, found in other proteins involved in RNA maturation. The other two domains bind tightly to the CBP20 subunit. Four residues on CBP20 are crucial for cap binding, and the authors propose that both subunits might be required owing to ?the poor stability of folded CBP20 in the absence of the CBP80?.

Translocation

Ssh1p determines the translocation and dislocation capacities of the yeast endoplasmic reticulum.

Wilkinson, B. M., Tyson, J. R. & Stirling, C. J. Dev. Cell 1, 401?409 (2001) [Contents page]

Translocation across the endoplasmic reticulum (ER) membrane requires the Sec61 translocon. The largest component of this complex is the Sec61 protein, which spans the ER bilayer ten times. The Sec61 homologue Ssh1 has been shown to interact with ribosomes, leading to speculation that it could act as a cotranslational translocon. This study of Δssh1 mutant cells supports such a function for Ssh1, identifying it as a component of a second, functionally distinct, translocon.