Figure 2.

Major mRNA degradation pathways. Deadenylation is the first event observed during most major mRNA decay processes. Deadenylation is biphasic with the first step catalyzed by the PAN2–PAN3 complex (blue–purple); the second step is mediated by CCR4-CAF1 (blue–aqua). After deadenylation, the mRNA is either decapped (yellow) and then rapidly degraded in the 5’ to 3’ direction by Xrn1 (aqua), or alternatively, the body of the mRNA can be degraded in the 3’ to 5’ direction by the exosome (blue). In specific cell types, deadenylated mRNAs can be stored as translationally inactive molecules (not shown).