Molecular recognition of mRNA 5' cap by 3' poly(a)-specific ribonuclease (PARN) differs from interactions known for other cap-binding proteins.

The mRNA 5′ cap structure plays a pivotal role in coordination of eukaryotic translation and mRNA degradation. Poly(A)-specific ribonuclease (PARN) is a dimeric exoribonuclease that efficiently degrades mRNA 3′ poly(A) tails while also simultaneously interacting with the mRNA 5′ cap. The cap binding amplifies the processivity of PARN action. We used surface plasmon resonance kinetic analysis, quantitative equilibrium fluorescence titrations and circular dichroism to study the cap binding properties of PARN.