Every RNA polymerase II transcript receives a 5′-end 7-methylguanosine (m7G) cap, which is rapidly bound by the nuclear cap–binding complex (CBC). Two recent studies now reveal that the CBC associates with a variety of effector proteins that enable it to interrogate nascent RNA, discriminating between distinct RNA subclasses and routing them either toward distinct maturation pathways or toward decay. Thus, the CBC has an early role in policing cellular RNA.
- Michaela Müller-McNicoll
- Karla M Neugebauer