FIGURE 4.

The CA-rich RNA elements are bound by hnRNP L, a mediator of CaMKIV-regulated splicing through CA repeats. A, 13-nt elements in the RNA probes made from the kinase-responsive clones as indicated. Control probe CG is from the gene PRKDC with its CACACA motif mutated to CGCGCG; mCaRRE1 in DUP175 is a positive control for hnRNP L binding. B, hnRNP L binds to the RNA probe C42 containing the CACAT motif as in mCaRRE1. HeLa nuclear extracts were subjected to UV-cross-linking with [α-³²P]CTP-labeled RNA probes (left), and 6 times of the nuclear extracts cross-linked to C42 were immunoprecipitated with the anti-hnRNP L antibody 4D11 (right). C, hnRNP L binds to the RNA probes containing similar CA repeats but not the CG probe. Similar to those in B, HeLa nuclear extracts were cross-linked to RNA probes A3.15, C7, and CG, and immunoprecipitated with the antibody 4D11. The arrow pointing to the ∼62-kDa band below hnRNP L is specific for the A3.15 probe.