RNA recognition motif (RRM) found in UHM domain of 45 kDa-splicing factor (SPF45) and similar proteins
This subfamily corresponds to the RRM found in UHM domain of 45 kDa-splicing factor (SPF45 or RBM17), poly(U)-binding-splicing factor PUF60 (FIR or Hfp or RoBP1 or Siah-BP1), and similar proteins. SPF45 is an RNA-binding protein consisting of an unstructured N-terminal region, followed by a G-patch motif and a C-terminal U2AF (U2 auxiliary factor) homology motifs (UHM) that harbors a RNA recognition motif (RRM), also termed RBD (RNA binding domain) or RNP (ribonucleoprotein domain) and an Arg-Xaa-Phe sequence motif. SPF45 regulates alternative splicing of the apoptosis regulatory gene FAS (also known as CD95). It induces exon 6 skipping in FAS pre-mRNA through the UHM domain that binds to tryptophan-containing linear peptide motifs (UHM ligand motifs, ULMs) present in the 3' splice site-recognizing factors U2AF65, SF1 and SF3b155. PUF60 is an essential splicing factor that functions as a poly-U RNA-binding protein required to reconstitute splicing in depleted nuclear extracts. Its function is enhanced through interaction with U2 auxiliary factor U2AF65. PUF60 also controls human c-myc gene expression by binding and inhibiting the transcription factor far upstream sequence element (FUSE)-binding-protein (FBP), an activator of c-myc promoters. PUF60 contains two central RRMs and a C-terminal UHM domain.