Figure 3. HnRNP C, YB-1 and hnRNP L bind to exon 10 of human MUSK.

(a, b) Mouse nucleotides are introduced into ESS5 (a) and ESS12 (b) of pH-wt to generate pH-mB5 and pH-mB12, respectively. RT-PCR of each mutated minigene in HeLa cells is compared with that of pH-wt. Primer positions are shown by arrows. (c) Sequences of ESS5 RNA probes carrying human (H-B5), mouse (m-B5), and partially deleted (H-B5Δ5) sequences. (d)³²P-labeled H-B5 or m-B5 RNA probe was incubated in the presence or absence of HeLa nuclear extract (NuEX) and resolved on a native polyacrylamide gel to observe free and protein-bound RNA species (arrows). (e) Coomassie blue staining of RNA affinity-purified products from HeLa nuclear extract using the indicated biotinylated RNA probes. Three proteins of ~70, ~50, and ~40 kDa (arrows) are differentially associated with H-B5 compare to m-B5 and H-B5Δ5. Mass spectrometry analysis revealed that the three proteins are HnRNP L (L), YB-1, and hnRNP C (C). (f) Immunoblotting (IB) of RNA affinity purified proteins in panel (e) with the indicated antibodies.