Molecular basis for the distinct cellular functions of the Lsm1–7 and Lsm2–8 complexes

The structure of S. pombe Lsm1–7 bound to RNA. (A) Overview of Lsm1–7 bound to UUUUA. (B) Overview of Lsm1–7 bound to AUUUUG. (C) RNA-binding interface of Lsm1–7 bound to UUUUA, showing that four uracil bases bind in the same manner as in the Lsm2–8 complex, while the adenosine binds into non-Sm pocket in Lsm5. (D) Lsm1–7 bound to AUUUUG, showing a similar binding mechanism as in C. (E,F) Detailed view of the non-Sm Lsm5 binding pocket occupied by adenine or guanine. In both cases, the 3′ purine is coordinated through hydrogen bonding with Lsm5–Asn66 and stacking with Lsm5–Asn68.