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Deep inside the cell As researchers explore the mechanisms at work in the cell, the basic building block of life, they reveal unsuspected mechanisms, from the tiniest details of neuron communication to “suicide recombination” in B cells. 18 Stem cells: life after death For the first time ever, researchers have observed, both in humans and mice, the ability of stem cells in muscles and bone marrow to enter into a dormant state lasting several days post mortem. This ability to reduce metabolic activity allows stem cells to preserve their potential for cell division and reactivate it as soon as the conditions in their environment become favorable again. This discovery could in particular address the shortage of cells available for cell therapy. Nature Communications June 2012 The genetic information contained in messenger RNA (in yellow) is decoded in the ribosome (in grey and purple). When antibody genes act like kamikaze --------------------------------------------------------------------------------------- Immune cells have the unique ability to reorganize and cleave their chromosomes. This ability allows B lymphocytes to produce a wide variety of antibodies. A French team has discovered a hitherto unknown type of chromosome cleavage: they have shown that immune B cells can cleave all the antibody genes and delete them. Since the cells cannot survive without expressing these genes, this is in fact a “suicide recombination” that is fatal for the cells involved. This discovery may shed light on how such suicide recombinations could facilitate the survival of protective cells and eliminate those that have no purpose or are harmful to the body (such as cells causing allergies, autoimmune diseases and cancer). Controlling this phenomenon might also make it possible to deliberately induce “suicide” in tumor cells or in cells responsible for immune disorders. Science April 2012 online Protein synthesis: how the ribosome selects the right amino acids During protein synthesis, translation of genetic information into proteins is carried out by complex cell structures called ribosomes, which select the transfer RNA (tRNA) carrying the right amino acids. By using structural data, French researchers have shown that the ribosome imposes strict geometric constraints on the tRNA, which enables it to distinguish between right and wrong tRNA, thus ensuring accurate decoding. Nature March 2012 online A year at CNRS 2012


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