Assessing messenger RNA decapping in cellular extracts.

Removal of the 5' cap from a messenger RNA (mRNA) is an integral part of all mRNA decay pathways and can be a highly regulated event. Assays designed to assess decapping in vitro need to effectively resolve four products of mRNA decay: 7meGpppG produced by 3'-5' shortening of the transcript by the exosome, 7meGMP produced by the scavenger decapping enzyme DcpS acting on the product of exosomal decay, 7meGDP produced by the Dcp1/2 decapping enzyme, and free phosphate, which can be generated by phosphatases in the extract acting upon either of the two products of decapping noted above. We have outlined both thin-layer chromatography and acrylamide-gel based approaches that can be used to assess decapping activities.