Serine/threonine protein kinase involved in both mRNA surveillance and genotoxic stress response pathways. Recognizes the substrate consensus sequence [ST]-Q. Plays a central role in nonsense-mediated decay (NMD) of mRNAs containing premature stop codons by phosphorylating UPF1/RENT1. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Expressed during early cleavage, gastrulation and at 1 day post-fertilization. Autophosphorylated. Morpholino knockdown results in reduced slc24a5 expression in wild-type embryos however expression is still detectable in the body and retinal pigment epithelium (PubMed:19414594). In 50% of the embryos expression of slc24a5 is restricted to the retina (PubMed:19414594). Belongs to the PI3/PI4-kinase family.