Extended Data Fig. 1: Secondary structures of human pre-tRNA^Gln, pre-mascRNA and mascRNA and crystal structures of human mascRNA and pre-mascRNA.

a, b, Secondary structures of pre-tRNA^Gln (a) and pre-mascRNA (b). Both RNAs contain 30-nucleotides (nts) of natural 5′-leader and 3′-trailer sequences (red). RNase P and ELAC2 cleavage sites are indicated by blue arrowheads. c, Secondary structure of the crystallization construct corresponding to the post-cleavage mascRNA prior to 3′ CCA addition. d, Front, back, and side views of mascRNA structure as in c, colored as Fig. 1. e, Secondary structure of the crystallization construct that corresponds to the pre-mascRNA. The 9-base pair (bp) acceptor stem extension is shown in grey. To facilitate crystallization, the original 8-bp AU-rich extended acceptor stem was extended by 1-bp, its GC content increased, and the bulged A removed. f, Front, back, and side views of the pre-mascRNA structure as in e, colored as Fig. 1.