Decapping is a central step in eukaryotic mRNA turnover. Recent studies have 
identified several factors involved in catalysis and regulation of decapping. 
These include the following: an mRNA decapping complex containing the proteins 
Dcp1 and Dcp2; a nucleolar decapping enzyme, X29, involved in the degradation of 
U8 snoRNA and perhaps of other capped nuclear RNAs; and a decapping 'scavenger' 
enzyme, DcpS, that hydrolyzes the cap structure resulting from complete 3'-to-5' 
degradation of mRNAs by the exosome. Several proteins that stimulate mRNA 
decapping by the Dcp1:Dcp2 complex co-localize with Dcp1 and Dcp2, together with 
Xrn1, a 5'-to-3' exonuclease, to structures in the cytoplasm called processing 
bodies. Recent evidence suggests that the processing bodies may constitute 
specialized cellular compartments of mRNA turnover, which suggests that mRNA and 
protein localization may be integral to mRNA decay.