THE MAIZE CHROMOSOMAL HMGA PROTEIN RECOGNIZES STRUCTURAL FEATURES OF DNA AND INCREASES DNA FLEXIBILITY

The abundant maize high-mobility group protein HMGa belongs to the chr omosomal, non-histone proteins and consists of a basic region containi ng the HMG-box DNA-binding domain and a highly acidic carboxy-terminal tail. The full-length HMGa protein and a truncated version lacking th e acidic tail were synthesized in Escherichia coli and tested for thei r ability to induce DNA-bending in a ligase mediated circularization a ssay with short DNA fragments. It is shown that the recombinant HMGa p rotein as well as its truncated form efficiently cause circularization of the tested DNA fragments without an obvious requirement for stable DNA-binding. They bind furthermore preferentially to ATT-rich linear DNA or bent DNA structures such as four-way junctions and DNA minicirc les. The DNA-binding properties and the ability to increase DNA flexib ility suggest a general role of the HMGa protein in assisting the form ation of nucleoprotein complexes, possibly by facilitating interaction s of proteins bound to adjacent DNA sites.