Helicases are ubiquitous ‘molecular motor’ enzymes that disrupt nucleic acid (NA) helices and NA-protein interactions. Despite the key roles of helicases in many cellular processes and diseases, their target repertoires and the determinants of their functional specialization are often unknown. Scientists from the ‘RNA remodeling’ group of CBM have developed a new screening scheme, Helicase-SELEX, to elucidate helicase substrate requirements and find natural or synthetic helicase substrates in large NA sequence libraries. Using the transcription termination Rho helicase as prototype, the CBM scientists have discovered ~3300 functional substrate sequences in Escherichia coli, thereby providing the first detailed map of Rho utilization (Rut) sites at genome scale. Further, they have shown that inclusion of a Rho cofactor (NusG) in the selection scheme can modulate the H-SELEX outcome and help probe specificity determinants at global scale. Finally, they have used H-SELEX to evolve synthetic Rut sequences operating as riboswitches able to elicit Rho activity in vitro and in vivo only in presence of an orthogonal cofactor (serotonin). Thus, Helicase-SELEX is a versatile new approach to characterize or exploit helicases for fundamental or biotechnology purposes.

The CNRS Institute of Chemistry has reported this new original screening approach on its website