Stress granules (green) pass mRNAs not protected by ZBP1 to processing bodies (red) for destruction.

Stressed-out cells pack away all but their crucial messenger RNAs for better times. The zipcode binding protein (ZBP1) functions as a preservative for the stored RNA, as Stöhr et al. report on page 527. By sheltering some cached molecules, the protein might help cells to recover quickly once conditions improve.

Heat, reactive oxygen species, and other harsh stimuli shut down production of proteins not needed for dealing with the stress. Cells switch off the nonessential proteins by diverting their mRNAs into stress granules. These structures can hold onto the strands or pass them to processing bodies for digestion. Researchers don't know why some mRNAs escape break-down.

ZBP1 stabilizes several RNAs in the cytoplasm, prompting Stöhr et al. to investigate whether it does the same in the stress granules. The protein doesn't dictate which mRNAs gather in the organelles, the researchers found, but it does influence what happens to them. Knocking down ZBP1 increases the deterioration of four RNAs that ZBP1 binds but does not affect the decay of non-ZBP1 targets.

Depleting ZBP1 also reduces the amount of mRNA that remains in the storage granules. The missing strands presumably depart for processing bodies or other sites where they are chopped up.