PSC Frontier Seminar series
Title: De-mixing of Genome Surveillance
Speaker: Prof. Jungnam Cho, CAS Center for Excellence in Molecular Plant Sciences, Shanghai, China; CAS-JIC Centre of Excellence for Plant and Microbial Science, Shanghai, China; University of Chinese Academy of Science, Beijing, China.
Time: 10:00 am
Day/Date: April 6th, 2021 (Tuesday)
Host: Prof. Chanhong Kim
Venue: PSC Auditorium
Transposable elements (TEs, transposons) are mobile DNAs that can cause fatal mutations. To suppress their activity, host genomes deploy small interfering (si) RNAs that trigger and maintain their epigenetic silencing. In plants, while 24-nt siRNAs mediate RNA-directed DNA methylation (RdDM) to reinforce the silent state of TEs, activated or naïve transposons give rise to 21- or 22-nt siRNAs by the RNA-DEPENDENT RNA POLYMERASE 6 (RDR6)-mediated pathway, triggering both RNAi and de novo DNA methylation. This process, which is called RDR6-RdDM, is critical for the initiation of epigenetic silencing of active TEs; however, their specific recognition and selective processing of siRNAs remain elusive. In this seminar I will present our latest work demonstrating that plant transposon RNAs undergo frequent ribosome stalling caused by their unfavourable codon usage. Ribosome stalling subsequently induces RNA truncation and localization to cytoplasmic siRNA bodies, which are both essential prerequisites for RDR6 targeting. In addition, SUPPRESSOR OF GENE SILENCING 3 (SGS3), the RDR6-interacting protein, exhibits phase separation both in vitro and in vivo through its prion-like domains, implicating the role of liquid-liquid phase separation in siRNA body formation. Our study provides novel insight into the host recognition of active TEs, which is important for the maintenance of genome integrity.
The seminar will be delivered in English.