Contributed by Joan A. Steitz, February 22, 2021 (sent for review December 29, 2020; reviewed by Elena Conti, Karin Musier-Forsyth, and Hongwei Wang)RNA triple helices were characterized in vitro over 60 y ago, but only recently implicated in diverse biological activities. The element for nuclear expression (ENE) protects RNA from degradation via triplex formation with the poly(A) tail on the 3ʹ ends of cellular RNAs. ENEs appear in diverse genomes, including a category containing two ENEs separated by a double-stranded region (dENEs). Using structure probing, SAXS, and cryo-EM, we show...…Contributed by Joan A. Steitz, February 22, 2021 (sent for review December 29, 2020; reviewed by Elena Conti, Karin Musier-Forsyth, and Hongwei Wang)RNA triple helices were characterized in vitro over 60 y ago, but only recently implicated in diverse biological activities. The element for nuclear expression (ENE) protects RNA from degradation via triplex formation with the poly(A) tail on the 3ʹ ends of cellular RNAs. ENEs appear in diverse genomes, including a category containing two ENEs separated by a double-stranded region (dENEs). Using structure probing, SAXS, and cryo-EM, we show...WW…