When stressed, cells reduce protein synthesis to conserve energy and promote repair. In some mammalian cells, including neurons, stress leads to the formation of inactive clusters of ribosomes called disosomes. These disomes are formed by the pairing of two ribosomes through the homotypic interaction of the ES31Lb ribosomal RNA expansion segment. The ES31Lb interaction is both necessary and sufficient for the formation of disomes. This property gives brain cells an advantage in growth and resistance to stress. ES31Lb is predicted to homodimerize in approximately 20% of chordates, including variants in chicken and human. Cryo-electron tomography in chicken revealed an interaction between ES31Lb and ES9La in tetrasomes. This mechanism controls the reorganization of ribosomes during the stress response of animal cells.[1]