Tweaking cartwheel and centriole symmetry by rational SAS-6 engineering

Talk 2  of the day, by Michel STEINMETZ  from the Paul Scherrer Institute, Department of Chemistry and Biology, Laboratory of Biomolecular Research, Villigen CH,  presents studies on how SAS-6 engineering effects Cartwheel and centriole symmetry

• In most species newly formed centrioles are organized around a 9-fold symmetric ‘cartwheel’ structure established by protein SAS-6
• They challenged the Scaffold model, that postulates cartwheel is formed first and dictates the assembly of 9 fold symmetric microtubule wall
• To do that experiments were performed to challenge this master role of the cartwheel by mutating SAS-6 to change cartwheel symmetry
• The oligomers formed by various SAS-6 mutants were characterized in vitro using a combination of biophysical and structural methods, and the impact on symmetry changing mutations on cartwheels was assessed in Chlamydomonas and human cells
• Independent model: Their findings reveal that cartwheel and microtubule wall operate in an independent manner to establish the 9-fold symmetric architecture of centrioles.