報告題目：A new class of noncoding Y RNAs act as tethers and gates: insights from prokaryotes.

報 告  人：Dr.XINGUO CHEN

Department of Cell Biology

Yale University School of Medicine

報告時間：11月14日 15:30-16:30

報告地點：閔行校區文選醫學大樓217會議室

聯 系  人⇨：王朝霞 This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

報告摘要

The noncoding RNAs known as Y RNAs were discovered because they bind the Ro60 autoantigen, a ring-shaped protein that is a major target of autoantibodies in patients with systemic lupus erythematosus and Sjögren’s syndrome. Because Ro60 also binds misfolded ncRNAs in some animal cell nuclei, we have proposed that Ro60 functions in RNA surveillance. Structural and biochemical studies suggest that Y RNAs function as as gates to regulate other RNAs access to Ro60. Consistent with this hypothesis, we recently discovered that a Ro60 ortholog in the bacterium Deinococcus radiodurans is tethered by Y RNA to the exoribonuclease polynucleotide phosphorylase, forming a ribonucleoprotein machine specialized for structured RNA degradation (Chen et al, Cell 153:166-177, 2013). However, while recognizable Ro60 orthologs are encoded in approximately 5% of sequenced bacterial genomes, Y RNAs have only been detected in two bacteria, making it unclear whether these RNAs are common Ro60 partners. To determine whether additional Y RNAs are present in bacteria and to identify conserved structural features, we coupled homology searches with biochemical validation of specific candidates. We report that bacterial Y RNAs are encoded adjacent to Ro60 in more than 250 bacteria and phages. Remarkably, at least one Y RNA in each species contains a domain that strikingly resembles tRNA. These domains contain modified nucleotides at positions characteristic of tRNAs and are substrates for several enzymes that act on tRNAs. Our studies identify a new class of noncoding RNAs that mimic tRNAs and confirm the importance of these RNAs, both as Ro60 partners and in bacterial physiology.