RNA recognition motif 2 (RRM2) found in vertebrate serine/arginine-rich splicing factor 4 (SRSF4)
This subgroup corresponds to the RRM2 of SRSF4, also termed pre-mRNA-splicing factor SRp75, or SRP001LB, or splicing factor, arginine/serine-rich 4 (SFRS4), a splicing regulatory serine/arginine (SR) protein that plays an important role in both constitutive splicing and alternative splicing of many pre-mRNAs. For instance, it interacts with heterogeneous nuclear ribonucleoproteins, hnRNP G and hnRNP E2, and further regulates the 5' splice site of tau exon 10, whose misregulation causes frontotemporal dementia. SFRS4 also induces production of HIV-1 vpr mRNA through the inhibition of the 5'-splice site of exon 3. In addition, SRSF4 activates splicing of the cardiac troponin T (cTNT) alternative exon by direct interactions with the cTNT exon 5 enhancer RNA. SRSF4 can shuttle between the nucleus and cytoplasm. It contains an N-terminal RNA recognition motif (RRM), also termed RBD (RNA binding domain) or RNP (ribonucleoprotein domain), a glycine-rich region, an internal region homologous to the RRM, and a very long, highly phosphorylated C-terminal RS domains rich in serine-arginine dipeptides.