structural characterization of the CBC PHAX RNA complex

The nuclear cap-binding complex (CBC) binds to the 5' cap of nascent Pol II transcripts and co-ordinates their co-transcriptional maturation, transport or degradation. CBC with its partner PHAX form a mutually exclusive complex antagonizing diverse ‘classifier’ factors that promote either a productive or a degradative outcome. Using the AlphaFold-DB prediction of isolated PHAX (AF-Q9H814) and sequence alignments and biochemical assays, we identified conserved residues potentially lying within a minimal CBC binding region. We aim to challenge our hypothesis by obtaining a 3D structure of the CBC-PHAX-RNA complex, to inform on the critical co-transcriptional RNA fate determination process.