UCN2 and influenza: Because of the structural similarity of the active sites of LC180 and PA-Nter, the experiments were guided by our previous work on influenza PA-Nter and used two of the same RNAs, a single-stranded, unstructured 51 nucleotide (nt) U-rich RNA and a highly structured 110 nt RNA, SRP Alu RNA as well as ssDNA [13].