SPF45/RBM17-dependent, but not U2AF-dependent, splicing in a distinct subset of human short introns

Abstract Human pre-mRNA introns vary in size from under fifty to over a million nucleotides. We searched for essential factors involved the splicing of human short by screening siRNAs against 154 nuclear proteins. The activity was assayed with model HNRNPH1 containing 56-nucleotide intron. identify known alternative regulator SPF45 (RBM17) as constitutive factor that is required splice out this 56-nt Whole-transcriptome sequencing SPF45-deficient cells reveals efficient many introns. To initiate spliceosome assembly on intron truncated poly-pyrimidine tract, U2AF-homology motif (UHM) competes U2AF 65 (U2AF2) binding UHM-ligand (ULM) U2 snRNP protein SF3b155 (SF3B1). propose distinct subset depends but not heterodimer.