D. Interaction of AAR2 and PRP8 in human cells. HA‑tagged PRP8 (aa1755-2335) was co-expressed in HEK293 cells with either wildtype AAR2, AAR2(S284A) or AAR2(S284E) mutant versions. Immunoprecipitation of PRP8 led to a co-precipitation of wild typeAAR2 and phospho-null AAR2(S284A). In contrast, the phospho-mimicry AAR2(S284E) version did not bind PRP8. 