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Abstract
Deadenylation of eukaryotic mRNA is a mechanism critical for mRNA function by influencing mRNA turnover and efficiency of protein synthesis. Here, we review poly(A)-specific ribonuclease (PARN), which is one of the biochemically best characterized deadenylases. PARN is unique among the currently known eukaryotic poly(A) degrading nucleases, being the only deadenylase that has the capacity to directly interact during poly(A) hydrolysis with both the m7G-cap structure and the poly(A) tail of the mRNA. In short, PARN is a divalent metal-ion dependent poly(A)-specific, processive and cap-interacting 3′–5′ exoribonuclease that efficiently degrades poly(A) tails of eukaryotic mRNAs. We discuss in detail the mechanisms of its substrate recognition, catalysis, allostery and processive mode of action. On the basis of biochemical and structural evidence, we present and discuss a working model for PARN action. Models of regulation of PARN activity by trans-acting factors are discussed as well as the physiological relevance of PARN.
Acknowledgements
We are grateful to all our collaborators throughout the years of our studies of PARN. In particular, we acknowledge graduate students (Anders Åström, Jonas Åström, Yan-Gou Ren, Sussie Stier, Ann-Charlotte Thuresson, Helena Nordvarg, Pontus Larsson and Lei Liu Conze) and post-doctoral fellows (Christina Kyriakopoulou, Catherine Phillips, Javier Martinez, Nikolaos Balatsos, Jens Schuster, Andrea Stauffiger, Magnus Lindell and Harri Ahola) that have been members of the lab since the early 90s and actively participated in discussions and studies of PARN. We gratefully acknowledge Leif Kirsebom and Jyoti Chattopadhyaya for comments and suggestions on the manuscript, and Terese Bergfors for skillful linguistic revision of the manuscript.