Poster abstracts
Poster number 128 submitted by Paul Kremer
Unraveling the molecular details of risdiplam binding
Paul Kremer (Biophysics Department, Medical College of Wisconsin), Yaqiang Wang (Biophysics Department, Medical College of Wisconsin)
Abstract:
Targeting RNA with small-molecule therapeutics is a growing area of interest in drug discovery. In 2020, risdiplam became the first FDA-approved small molecule therapeutic found to interact directly with RNA. Risdiplam treats spinal muscular atrophy which is caused by a loss of function of the SMN1 gene. SMN2 encodes the same protein as SMN1, but due to a weak 5’ spilce site, produces mostly non-functional protein. The existing theory of risdiplam binding is that it binds in the buldged-A pocket of the SMN2 weak 5’ splice site, improving alternative splicing efficiency; however, the current data does not provide sufficient detail to establish this mechanism. To further characterize the binding pocket, we designed an extended RNA construct tethered by a tetraloop. Our construct reproduced findings from previous studies, which used a duplexed construct, while providing atomic-level details of the binding pocket, thus establishing the buldged-A mechanism. Preliminary data show that mutations to the bulged-A and adjacent region do not prevent risdiplam binding. Beyond characterizing the binding pocket, we are using NMR spectroscopy to determine the structure of the risdiplam-bound RNA construct. This study provides new insight into the molecular details of risdiplam–RNA recognition and may aid structure-based drug design for other weak 5’ splicing site mutations
Keywords: Risdiplam, weak 5 splice site