THE HUMAN S-MU-BP-2, A DNA-BINDING PROTEIN-SPECIFIC TO THE SINGLE-STRANDED GUANINE-RICH SEQUENCE RELATED TO THE IMMUNOGLOBULIN-MU CHAIN SWITCH REGION

We have cloned the cDNA encoding the human homologue of Smubp-2, which binds to single-stranded DNA with 5'-phosphorylated guanine-rich sequ ences related to the immunoglobulin mu chain switch (S(mu)) region. Th e deduced amino acid sequences of the mouse and human Smubp-2 are 76.5 % homologous and contain motifs conserved among helicases. We have ide ntified a domain essential for DNA binding at residues 638-786. The bi nding domain is less conserved (63% homologous) than the putative cata lytic domain of N-terminal half containing most of the helicase motifs (85% homologous). The human and mouse SmuAbp-2 have similar, although slightly different, binding specificities. Although the mouse Smubp-2 preferentially binds to the mouse S(mu) motif (GGGGT), the human Smub p-2 binds equally well to the human (GGGCT) and mouse S(mu) motifs. Th e human Smubp-2 gene was mapped to chromosome 11 q13.2-q13.4 by in sit u hybridization.