Poster abstracts
Poster number 13 submitted by Sukanya Srinivasan
Auxiliary domains of the mammalian DEAH/RHA helicase DHX36 work in concert with the helicase core domains to remodel RNA structures.
SUKANYA SRINIVASAN (Center for RNA science and Therapeutics, Case Western Reserve University), Zhonghua Liu (Department of Pathology, Case Western Reserve University), Tsan Sam Xiao (Department of Pathology, Case Western Reserve University), Eckhard Jankowsky (Center for RNA science and Therapeutics, Case Western Reserve University)
Abstract:
The DEAH/RHA helicase DHX36 is linked to DNA and RNA G-quadruplex structures and to AU-rich element (ARE) - mediated mRNA deadenylation and decay. In vitro, DHX36 resolves DNA and RNA G-quadruplex structures and unwinds RNA duplexes. However, the molecular basis for DHX36-mediated remodeling of RNA quadruplex and duplex structures remains poorly understood and important biochemical features of DHX36 substrate specificity remain unclear. To address these questions, we combined structural and biochemical analyses of mouse DHX36. We have solved the crystal structure of DHX36 in complex with ADPNP (a non-hydrolysable ATP analog). The structure provides a conformational snapshot of a “closed” nucleotide-bound form of DHX36. It reveals an overall architecture similar to that previously observed for other DEAH/RHA helicases. Biochemical experiments demonstrate that at saturating DHX36 concentration, unwinding rate constants are 4 fold higher for quadruplexes than for duplex structures. In addition, the functional affinity of DHX36 for quadruplexes is more than 20 fold higher than that for duplex structures. The data thus reveal that DHX36 preferentially binds and remodels RNA quadruplex structures, compared to duplex structures. We further show that the N-terminal DSM domain functions not only as a quadruplex binding adaptor, but also promotes the remodeling of both, duplex and quadruplex structures. In addition, we demonstrate that two previously uncharacterized DHX36 regions, a 5’-β-hairpin in the helicase core, and the C-terminal OB-fold domain are essential for the ability of DHX36 to bind and remodel both, quadruplex and duplex structures. Collectively, our data reveal that the auxiliary domains of DHX36 work in conjunction with the helicase core to remodel RNA structures.
Keywords: DHX36, RNA G-quadruplex, RNA duplex