Stressed out! Effects of environmental stress on mRNA metabolism.

Exposure of yeast cells to environmental stresses can disrupt essential intracellular processes, especially those carried out by large macromolecular complexes. The production of mature, translatable mRNAs is most sensitive to stress owing to the inhibition of messenger RNA splicing and alterations in the export of mRNA from the nucleus. Changes in the cytoplasmic pools of mRNAs also occur following exposure to stress conditions. Messenger RNAs accumulate in discrete cytoplasmic foci such as processing bodies and stress granules. These dynamic changes in RNA metabolism, following exposure to stress, ensure the preferential production and export of heat-shock mRNAs and the sequestering of general cellular mRNAs in the nucleus or in cytoplasmic foci, thus allowing for a redirection of the translational machinery to encode stress proteins, which aid in cellular recovery following stress. Stress proteins, such as Hsp70p and Hsp104p, have been shown to play a direct role in the repair of macromolecular complexes involved in RNA metabolism in yeast cells, thus ensuring that the cell returns to homeostasis.