Complemented palindrome small RNAs first discovered from SARS coronavirus

Chang Liu; Ze Chen; Wenyuan Shen; Deshui Yu; Siyu Li; Yue Hu; Haishuo Ji; Wenjun Bu; Qingsong Wang; Shan Gao

The first discovered cpsRNA named SARS-CoV-cpsR-22 contained 22 nucleotides perfectly 76 matching its reverse complementary sequence. In our previous study of mitochondrial genomes, we had 77 reported for the first time a 20-nt palindrome small RNA (psRNA) named hsa-tiR-MDL1-20 [10]. The 78 biological functions of hsa-tiR-MDL1-20 had been preliminarily studied in our previous study, while the 79 biological functions of SARS-CoV-cpsR-22 were still unknown. In this study, we compared the features of 80 siRNA duplexes induced by mammal viruses with those induced by plant and invertebrate viruses and found 81 that siRNA duplexes induced by mammal viruses had significantly lower percentages of total sequenced 82 reads and it seemed that they were only produced from a few sites on the virus genomes. One possible 83 reason could be a large proportion of sRNA-seq data is from other small RNA fragments caused by the 84 presence of a number of dsRNA-triggered nonspecific responses such as the type I interferon (IFN) 85 synthesis [11] . Another possible reason could be the missing siRNA duplexes or siRNA fragments functions 86 in cells by interaction with host RNAs or proteins. Based on this idea, we suspected that SARS-CoV-cpsR-87 22 could play a role in SARS-CoV infection or pathogenicity. Then, we performed RNAi experiments to test 88 the cellular effects induced by SARS-CoV-cpsR-22 and its segments. 89