# An intrinsically disordered region mediates RNA-binding selectivity and cellular activities of LARP6

## TL;DR

The study reveals how a disordered region in the LARP6 protein helps it selectively bind RNA, which is important for cancer cell functions.

## Contribution

The novel finding is that intrinsically disordered regions can modulate RNA-binding specificity by influencing structured domains.

## Key findings

- The N-terminal IDR of LARP6 broadens RNA footprints and enhances binding selectivity.
- IDRs modulate RNA access by restricting conformational flexibility of the La-module.
- IDR-mediated RNA selectivity is crucial for LARP6's role in cancer cell viability and invasion.

## Abstract

Intrinsically disordered regions (IDRs) are prevalent in RNA-binding proteins (RBPs), yet their roles in RNA interactions remain poorly defined. We examined RNA-binding regulation by structured and disordered regions of LARP6, an RBP with a diverse RNA-binding repertoire. Mass spectrometry-based RNA interaction mapping in living cells identified direct LARP6–RNA contacts within the structured La-module and its flanking IDRs. Mutagenesis and individual-nucleotide resolution UV-crosslinking and immunoprecipitation (iCLIP) revealed the La-module, but not the IDRs, as essential for LARP6 RNA binding. Deletion of the N-terminal IDR broadened LARP6 RNA footprints, uncovering a role in RNA-binding selectivity. This is achieved through a composite mechanism of restricting the conformational flexibility of the adjacent La-module, forming auxiliary contacts with the RNA, and modulating RNA access for binding. The IDR-mediated RNA-binding selectivity is critical for LARP6-mediated promotion of cancer cell viability and invasion. Our findings uncover a previously unrecognised critical function for IDRs in promoting selective RBP–RNA recognition, by affecting the binding specificity of their adjacent structured domains.

LARP6 is an EMT-associated RNA-binding protein with diverse RNA targets. Here, the authors show that the N-terminal disordered region of LARP6 promotes RNA-binding selectivity by modulating the adjacent La-module and forming auxiliary contacts with RNA.