Pat1 activates late steps in mRNA decay by multiple mechanisms

Significance In yeast, the majority of mRNAs is degraded in a 5′-3′ direction. This pathway requires the assembly of conserved protein complexes on the 5′ and 3′ termini of the mRNA after its poly(A) tail is removed. These decay complexes are poorly active in the absence of the Pat1 protein. We show how Pat1 enhances binding of the 3′ complex to RNA and activates the 5′ decapping complex using a combination of disordered and structured domains to promote distinct steps in mRNA decay. By activating cofactors, Pat1 may be able to regulate multiple aspects of mRNA metabolism.