Topoisomearse II is an essential enzyme in all organisms with several independent roles in DNA metabolism. Recently, it has been demonstrated that the C-terminal region of topoisomerases II is associated with hetero-logous protein-protein interactions in human and yeast. In this study, we identified that RTP1, a rat homologue of EIA binding protein BS69, is another topoisomerae II interacting protein by yeast two-hybrid screening. RTP1 has an E1A-binding domain and a MYND motif, which are known to be required for transcriptional regulation by binding to other proteins and interaction with the leucine zipper motif of topoisomerase II. The physical interaction between RTP1 and topoisomerase ll$alpha$ was examined by GST pull-down assay in vitro. The expression level of RTP1 peaks in S phase as that of topoisomerase ll$alpha$. These results suggest that the interaction between topoisomerase ll$alpha$ and RTP1 might play an important role in regulating the transcription of genes involved in DNA metabolism in higher eukaryotes.