Targeted protein proteolysis is increasingly understood to be an important general mechanism by which cells regulate protein levels — and consequently their functions at specific times. In eukaryotic cells, the main mechanism for such control involves the specific covalent modification by polyubiquitin, which labels target proteins for proteolysis and subsequent degradation. There are many know...

extinguished by the transfer. But the extent of the transformation is not yet clear. “It’s possible that what we are doing is turning everything into an oocyte,” says Gurdon. But he believes that oct4 expression is a good sign that the cells are at least headed toward becoming stem cells. Stem cell characteristics may develop only through sequential inductive events. But the optimists are hopin...

A definite increase in the percentage of reticulocytes occurs after exercise in animals previously kept to a sedentary life. Concomitant changes in the hemoglobin percentage, plasma-cell ratio, and red count offer evidence in addition to that already reported by the author of the occurrence of an increase in blood destruction under such circumstances. Replacement by transfusion of blood destroy...

Upon contact with their bacterial targets, neutrophils fire a barrage of antimicrobial peptides, sometimes releasing structures called neutrophil-associated extracellular traps, or NETs. In releasing their NETs, they commit suicide—unleashing their entire antibacterial arsenal via a specialized form of programmed cell death called netosis. Hakkim et al. (2011) now provide new insight into the m...

Important transitions in the cell cycle are regulated by ubiquitin-dependent degradation of specific proteins. Recent data indicate that cytokinesis is also regulated by proteolysis.

X-ray free-electron lasers have opened up the possibility of structure determination of protein crystals at room temperature, free of radiation damage. The femtosecond-duration pulses of these sources enable diffraction signals to be collected from samples at doses of 1000 MGy or higher. The sample is vaporized by the intense pulse, but not before the scattering that gives rise to the diffracti...

W HILE OUR NAtional leaders agonize abou t the threats in the Middle East from missiles, bombs, and automatic weapons that might fall into terrorist hands, they have remained eerily silent about the unlimited access to weapons of mass destruction in our own backyard. In a sickening recapitulation of terror wrought in schools, movie theaters, and malls, our nation grieves for the large number of...