A TOPOISOMERASE II-LIKE PROTEIN IS PART OF AN INDUCIBLE DNA-BINDING PROTEIN COMPLEX THAT BINDS 5' OF AN IMMUNOGLOBULIN PROMOTER

We previously identified a B cell-specific protein-DNA complex 5' of a n immunoglobulin it heavy chain promoter. The sequences to which this protein complex bound were required for induction of immunoglobulin mR NA levels with interleukin-5 + antigen. Further studies identified a s econd sequence 5' of these regulatory sequences that bound to both the nuclear matrix and to a similar interleukin-5 + antigen inducible pro tein complex. Therefore, we sought to identify the putative regulatory proteins that comprised this DNA-binding complex. In this study, we h ave used anti-topoisomerase II antibodies to demonstrate that one of t he proteins found in the interleukin-5 + antigen inducible complexes i s serologically related to topoisomerase II. To our knowledge, this is the first report where a topoisomerase II related protein participate s in an inducible mobility shifted protein-DNA complex. These data sug gest a model in which the enhanced immunoglobulin gene transcription o bserved after treatment with interleukin-5 + antigen might be explaine d by the induction of a protein complex that acts to relieve torsional stress along the gene.