One of the key early steps in splicing is recognition of the 5′ splice site by base-pairing to the U1 small nuclear RNA. Data now indicate that U1 can shift to recognize what had been designated as atypical 5′ splice sites, broadening the scope of what can be recognized as a functional splice site by the canonical machinery and thus impacting both splicing predictions and mechanism, as well as providing a potential mechanism underlying a puzzling mutation associated with pontocerebellar hypoplasia.
- Xavier Roca
- Adrian R Krainer
