THE MYB ONCOGENE PRODUCT INDUCES DNA-BENDING

The nuclear oncogene v-myb and its cellular counterpart c-myb code for proteins that bind to DNA in a sequence specific manner and act as re gulators of transcription. The Myb protein contains DNA binding and tr ansregulatory domains which are important for its function. The DNA bi nding domain of Myb protein has been shown to contain three imperfectl y conserved repeats of 50-52 aminoacids that constitute the amino term inal end. In this communication, we show that Myb protein induces conf ormational change in DNA after protein-DNA complex formation. Circular permutation assays indicate that Myb protein induces DNA bending at t he site of binding. Phasing analysis confirm the DNA bending and allow ed the detection of relative orientation of bend. Myb proteins which c omprise only DNA-binding domains either with three repeats or two repe ats also bend DNA in the same orientation as the larger proteins with both DNA-binding and transactivating domains. However, the transactiva ting region seems to influence the magnitude of bend angle. We used mo lecular modeling to analyse the structure of Myb-DNA complex formation resulting in the bending of DNA. Data presented here show that Myb pr otein, like other transcriptional regulators, bends DNA upon binding a llowing the interaction of regulatory elements.