The Argonaute-binding platform of NRPE1 evolves through modulation of intrinsically disordered repeats

Argonaute proteins are important effectors in RNA silencing, but they must interact with other cellular machinery to cause silencing. Ago hooks are a conserved linear motif responsible for interaction with Argonaute proteins, but little is know about the sequence surrounding these small motifs, which 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 more than 50 species, including dense sampling of two plant lineages. Our study demonstrates conservation of intrinsic disorder and repetitive character within the Ago-binding platform, but loss of sequence conservation. We reveal that loss of conservation is due to frequent expansions and contractions within tandem repeats, along with relaxed selection. Consequences and possible evolutionary drivers of this diversity will be discussed.