Ribosome cycling

Ribosome biogenesis consumes up to 80% of the energy of the cell. To prevent wastage of all of that energy, coordination with the cell cycle is vital. Both ribosome biogenesis and cell proliferation go awry when a the integrity of a three-protein complex (Nop7p-Erb1p-Ytm1p) in yeast is disrupted. Now on page 367, Hölzel et al. show that a homologous complex comprised of Pes1-Bop1-WDR12 exists in mammals and, like its yeast counterpart, relates cell cycle progression to ribosomal RNA processing.

Like Pes1 and Bop1, which have been characterized previously, Hölzel et al. find that WDR12 is up-regulated in response to c-myc expression and cell proliferation. Pes1, Bop1, and WDR12 copurified in immunoprecipitation experiments.

A link between ribosome biogenesis and the cell cycle may be provided by p53. This protein accumulates when the rRNA-encoding nucleolus...