RGG-motif protein Sbp1 is required for Processing body (P-body) disassembly

Abstract

RNA granules are conserved mRNP complexes that play an important role in determining mRNA fate by affecting translation repression and mRNA decay. Processing bodies (P-bodies) harbor enzymes responsible for mRNA decay and proteins involved in modulating translation. Although many proteins have been identified to play a role in P-body assembly, a bonafide disassembly factor remains unknown. In this report, we identify RGG-motif translation repressor protein Sbp1 as a disassembly factor of P-bodies. Disassembly of Edc3 granules but not the Pab1 granules (a conserved stress granule marker) that arise upon sodium azide and glucose deprivation stress are defective in{Delta} sbp1. Disassembly of other P-body proteins such as Dhh1 and Scd6 is also defective in{Delta} sbp1. Complementation experiments suggest that the wild type Sbp1 but not an RGG-motif deletion mutant rescues the Edc3 granule disassembly defect in{Delta} sbp1. We observe that purified Edc3 forms assemblies, which is promoted by the presence of RNA and NADH. Strikingly, addition of purified Sbp1 leads to significantly decreased Edc3 assemblies. Although low complexity sequences have been in general implicated in assembly, our results reveal the role of RGG-motif (a low-complexity sequence) in the disassembly of P-bodies.