We previously isolated RBP56 cDNA by PCR using mixed primers designed from the conserved sequences of the RNA binding domain of FUS/TLS and EWS proteins. RBP56 protein turned out to be hTAFII68 which was isolated as a TATA-binding protein associated factor (TAF) from a sub-population of TFIID complexes (Bertolotti A., Lutz, Y., Heard, D.J., Chambon, P., Tora, L., 1996. hTAFII68, a novel RNA/ssDNA-binding protein with homology to the proto-oncoproteins TLS/FUS and EWS is associated with both TFIID and RNA polymerase II. EMBO J. 15, 5022-5031). The RBP56/hTAFII68, FUS/TLS and EWS proteins comprise a sub-family of RNA binding proteins, which consist of an N-terminal Ser, Gly, Gln and Tyr-rich region, an RNA binding domain, a Cys2/Cys2 zinc finger motif and a C-terminal RGG-containing region. Rearrangement of the FUS/TLS gene and the EWS gene has been found in several types of malignant tumors, and the resultant fusion proteins play an important role in the pathogenesis of these tumors. In the present study, we determined the genomic structure of the RBP56/hTAFII68 gene. The RBP56/hTAFII68 gene spans about 37kb and consists of 16 exons from 33bp to 562bp. The longest exon, exon 15, encodes the C-terminal region containing 19 repeats of a degenerate DR(S)GG(G)YGG sequence. While the structure of the FUS/TLS gene has been reported previously, we determined the total DNA sequence of the FUS/TLS gene, consisting of 12kb. The RBP56/hTAFII68, FUS/TLS and EWS genes consist of similar numbers of exons. Comparison of the structures of these three genes showed that the organization of exons in the central part encoding a homologous RNA binding domain and a cysteine finger motif is highly conserved, and other exon boundaries are also located at similar sites, indicating that these three genes most likely originate from the same ancestor gene.