Talk abstracts
Talk on Friday 04:00-04:15pm submitted by Andrew Savidge
Neurodevelopmental disorder-linked Argonaute mutations permit incorrect miRNA loading
Andrew Savidge, Huaqun Zhang, Vishal Adhav, Geunyoung Sim, Audrey Kehling (Dept. of Chemistry and Biochemistry, The Ohio State University), Zhangfei Shen (Dept. of Biological Chemistry and Pharamacology, The Ohio State University), Tianmin Fu (Dept. of Pathology, UMass Chan Medical School), Kotaro Nakanishi (Dept. of Chemistry and Biochemistry, The Ohio State University)
Abstract:
Argonaute (AGO) proteins are the critical effectors of eukaryotic post-transcriptional gene regulation. AGO loads one strand of an 18-23 nt microRNA (miRNA) duplex as a guide to form the RNA-induced silencing complex (RISC), which silences a complementary messenger RNA. AGO syndrome is a newly classified neurodevelopmental disorder that is caused by point mutations in AGO proteins. Patients are identified in early childhood and have symptoms similar those with autism spectrum disorder. No structures of AGO syndrome mutants have been reported, and the basis of their neural dysfunction remains elusive. Here, we report the 3.4 Å cryo-electron microscopy (cryo-EM) structure of AGO1(ΔF180), a common AGO syndrome mutant. Despite the severe developmental defects caused by this mutation, the global structure is almost identical to that of AGO1(WT). We demonstrated that WT and mutant AGOs loaded with a 23-nt miR-20a guide bind to target RNAs with similar affinity, suggesting AGO1(ΔF180) behaves like the WT once the RISC is formed. However, our functional assays showed that AGO syndrome mutants fail to efficiently eject the passenger strand, slowing RISC maturation. As a result, AGO is prone to loading the incorrect strand of the duplex and is vulnerable to increased trimming of the 3′-end guide. Together, these results suggest erroneous miRNA guides underlie the pathogenic mechanism of AGO syndrome.
References:
1. A. Schalk, et al., De novo coding variants in the AGO1 gene cause a neurodevelopmental disorder with intellectual disability. J Med Genet 59, 965–975 (2021).
Keywords: noncoding RNA, human disease, structural biology