Purification and characterization of a nuclear DNA-binding factor complex containing topoisomerase II and chromosome scaffold protein 2.
In a search for factors that influence the process of erythroid differentiation at the molecular level, we have identified UB2, a nuclear protein factor that was originally observed for its ability to bind to a very specific and highly conserved sequence motif present in human, mouse, rabbit, and chicken beta-globin genes, as well as carbonic anhydrase I, c-myb, and the immunoglobulin heavy chain enhancer region. It was also observed for its appearance in undifferentiated but not differentiated mouse erythroleukemia cells. Purification of UB2 by DEAE-cellulose chromatography and repeated passages through a DNA affinity column, revealed a complex pattern with three major components of 170, 116, and 48 kDa, respectively. The 170-kDa protein was identified as topoisomerase (topo) II by Western blot analysis, catalytic assays, and antibody interference with UB2 binding. The complex topo II in UB2, however, has a more stringent sequence requirement for DNA binding than does topo II. The 116-kDa protein has been determined to be a proteolytic product of topo II. The chromosome scaffold protein 2 (135 kDa) copurified with UB2, and anti-scaffold protein 2 serum inhibited UB2 binding to DNA.
Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania 19104-4268.
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D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002460:Cell Line; D004247:DNA; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D004247:DNA; D004250:DNA Topoisomerases, Type II