Cell cycle

A DNA damage response pathway controlled by Tel1 and the Mre11 complex. Usui, T., Ogawa, H. & Petrini J. H. J. Mol. Cell 7, 1255?1266 (2001) [PubMed]

By examining checkpoint activation in Saccharomyces cerevisiae, the authors have defined a new DNA-damage response pathway controlled by the yeast ataxia-telangiectasia mutated (ATM) homologue Tel1, and the Mre11 complex. The Mre11 complex acts as the damage sensor, and its ability to repair double-stranded DNA breaks is enhanced by the pathway. According to the authors, these results indicate ?that the diverse functions of the Mre11 complex in the cellular DNA damage response are conserved in mammals and yeast?.

Technique

Short tandem repeat profiling provides an international reference standard for human cell lines. Masters, J. R. et al. Proc. Natl Acad. Sci. USA 98, 8012?8017 (2001) [PubMed]

Although there are many ways to detect cross-contamination between cell lines, none so far has been suitable for use as an international reference standard. Masters and colleagues now report the study, on 253 human cell lines, of a technique that they believe could fill this void ? short tandem repeat profiling. The profile is a simple numerical code that is reproducible between laboratories and inexpensive to generate.

Transcription

Structure of the histone deacetylase SIRT2. Finnin, M. S., Donigian, J. R. & Pavletich, N. P. Nature Struct. Biol. 8, 621?625 (2001) [PubMed]

SIRT2 is the human homologue of yeast Sir2, an NAD-dependent histone deacetylase that mediates transcriptional silencing at mating-type loci and telomeres. This report of the SIRT2 crystal structure ? at a resolution of 1.7 Å ? reveals an NAD-binding domain as well as a smaller domain composed of a helical module and a zinc-binding module. The helical module forms a pocket lined with hydrophobic residues that are conserved within the five classes of Sir2 proteins.

Cell adhesion

Requirement for C3G-dependent Rap1 activation for cell adhesion and embryogenesis. Ohba, Y. et al. EMBO J. 20, 3333?3341 (2001) [PubMed]

C3G is a guanine-nucleotide exchange factor for Rap1 that is now shown to be needed for adhesion and spreading. Embryonic fibroblast cells prepared from conditional C3G-deficient mice ? generated to overcome embryonic lethality of C3G knockouts ? show decreased adhesion and spreading, and also migrate faster. The authors showed that C3G is required for cell-attachment-mediated Rap1 activation, but that Rap1 activation alone isn't sufficient for spreading ? specific extracellular integrin matrices are needed.