Structure of frequency-interacting RNA helicase from Neurospora crassa reveals high flexibility in a domain critical for circadian rhythm and RNA surveillance

• Published in: PloS one Vol. 13; no. 5; p. e0196642
• Main Authors: Morales, Yalemi, Olsen, Keith J, Bulcher, Jacqueline M, Johnson, Sean J
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 02.05.2018; Public Library of Science (PLoS)
• Subjects: Adenosine triphosphate; Arches; BASIC BIOLOGICAL SCIENCES; Binding sites; Biochemistry; Biology and Life Sciences; Chromatography; Circadian Rhythm; Circadian rhythms; Conserved Sequence; Crystal structure; Crystallography; DNA helicase; Dynamic structural analysis; Gene expression; helicases; Homology; Kinases; Metabolism; Mutation; Neurospora; Neurospora crassa; Neurospora crassa - enzymology; Neurospora crassa - genetics; Neurospora crassa - physiology; Physical Sciences; Physiological aspects; Protein Conformation; Protein interaction; protein interactions; Protein structure; Protein-protein interactions; Proteins; Research and Analysis Methods; Ribonucleic acid; RNA; RNA - metabolism; RNA helicase; RNA Helicases - genetics; RNA Helicases - metabolism; RNA Helicases - physiology; RNA structure; Saccharomyces cerevisiae; Substrates; Surveillance; Yeast
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0196642

The FRH (frequency-interacting RNA helicase) protein is the Neurospora crassa homolog of yeast Mtr4, an essential RNA helicase that plays a central role in RNA metabolism as an activator of the nuclear RNA exosome. FRH is also a required component of the circadian clock, mediating protein interactions that result in the rhythmic repression of gene expression. Here we show that FRH unwinds RNA substrates in vitro with a kinetic profile similar to Mtr4, indicating that while FRH has acquired additional functionality, its core helicase function remains intact. In contrast with the earlier FRH structures, a new crystal form of FRH results in an ATP binding site that is undisturbed by crystal contacts and adopts a conformation consistent with nucleotide binding and hydrolysis. Strikingly, this new FRH structure adopts an arch domain conformation that is dramatically altered from previous structures. Comparison of the existing FRH structures reveals conserved hinge points that appear to facilitate arch motion. Regions in the arch have been previously shown to mediate a variety of protein-protein interactions critical for RNA surveillance and circadian clock functions. The conformational changes highlighted in the FRH structures provide a platform for investigating the relationship between arch dynamics and Mtr4/FRH function.