Characterization of a protein that binds to AT-rich DNA in a seed nuclear extract of winged bean (Psophocarpus tetragonolobus (L.) DC. cv. Ishigaki-4).

摘要

The organ-specific and temporally regulated expression of the genes for Kunitz chymotrypsin inhibitor-3 in winged bean is known to be governed by its 5' flanking region. Two nuclear factors that bind to AT-rich sequences in this region were detectedin gel retardation assays of seed nuclear extracts. The binding activity of one of these factors, band 1-forming factor, was inhibited by phosphorylation, as is the AT-binding protein ATBP-1 of tobacco, which functions as an activator of transcription.In addition, the binding of band 1-forming factor was reduced in the presence of a low concentration of the minor groove-binding dye, Hoechst 33258, suggesting that band 1-forming factor recognizes the minor groove of the probe, as does ATBP-1. The binding of another factor, band 3-forming factor, was also reduced by Hoechst 33258, but the binding activity of this factor was not affected by phosphorylation. During partial purification by gel-filtration and affinity chromatography, the binding activity of band 3-forming factor was cofractionated with a 75-ku (kDa) DNA-binding protein. These results indicate that band 3-forming factor is a new DNA-binding factor that recognizes the minor groove of AT-rich DNA.