title: The Argonaute-binding platform of NRPE1 evolves through modulation of intrinsically disordered repeats.
abstract: Argonaute (Ago) proteins are important effectors in RNA silencing pathways, but they must interact with other machinery to trigger silencing. Ago hooks have emerged as a conserved motif responsible for interaction with Ago proteins, but little is known about the sequence surrounding Ago hooks that must restrict or enable interaction with specific Argonautes. Here we investigated the evolutionary dynamics of an Ago-binding platform in NRPE1, the largest subunit of RNA polymerase V. We compared NRPE1 sequences from > 50 species, including dense sampling of two plant lineages. This study demonstrates that the Ago-binding platform of NRPE1 retains Ago hooks, intrinsic disorder, and repetitive character while being highly labile at the sequence level. We reveal that loss of sequence conservation is the result of relaxed selection and frequent expansions and contractions of tandem repeat arrays. These factors allow a complete restructuring of the Ago-binding platform over 50-60 million yr. This evolutionary pattern is also detected in a second Ago-binding platform, suggesting it is a general mechanism. The presence of labile repeat arrays in all analyzed NRPE1 Ago-binding platforms indicates that selection maintains repetitive character, potentially to retain the ability to rapidly restructure the Ago-binding platform.
authors.affiliation: The School of Plant Sciences, The University of Arizona, Tucson, AZ, 85721-0036, USA.
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Trujillo
authors.affiliation: The School of Plant Sciences, The University of Arizona, Tucson, AZ, 85721-0036, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Beilstein
authors.affiliation: The School of Plant Sciences, The University of Arizona, Tucson, AZ, 85721-0036, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Mosher
mesh_terms: D000595:Amino Acid Sequence; D060565:Argonaute Proteins / Q000378:metabolism*; D017124:Conserved Sequence; D019143:Evolution, Molecular; D020440:Gene Duplication; D064267:Intrinsically Disordered Proteins / Q000737:chemistry* / Q000378:metabolism*; D008954:Models, Biological; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D020449:Repetitive Sequences, Amino Acid; D013329:Structure-Activity Relationship
chemical_list: D060565:Argonaute Proteins; D064267:Intrinsically Disordered Proteins; D010940:Plant Proteins
keywords: Ago hook; Argonaute; RNA-directed DNA methylation; intrinsic disorder; polymerase V (Pol V); relaxed selection; repeat expansion; tandem repeat