During assembly of spliceosomal small nuclear ribonucleoproteins (snRNPs), the RNA-binding protein (RBP) Gemin5 recognizes the snRNP code and interacts with the large Gemin2–SMN complex. So et al. now find that Gemin2 also interacts with U1-70K, thereby conferring a preferential advantage on U1 snRNP assembly, and they extrapolate that SMN–Gemin2 serves a general ribonucleoprotein-exchange function.
- Megan Mayerle
- Christine Guthrie
