3 PROTEIN-FRACTIONS THAT BIND TO A NARROW REGION OF THE PROMOTER OF THE RIBOSOMAL-RNA GENE IN VICIA-FABA

We previously described the preparation of a protein fraction that bou nd to the promoter region of the rRNA gene of Vicia faba. We now descr ibe two additional protein fractions that interact with this DNA eleme nt. The three protein fractions have similar binding properties with t he exception of their binding stabilities. DNase I footprinting experi ments revealed that these protein fractions bind to a region that is l ocated about 60 bp upstream from the site of initiation of transcripti on. From methylation interference experiments and gel-retardation assa ys with mutated oligonucleotides, it was evident that the protein frac tions required the same residues for the formation of stable DNA-prote in(s) complexes. However, the three protein fractions were chromatogra phically distinguishable and the stability of their binding to DNA was different. Although the functions of these fractions are still unknow n, the fact that several protein fractions can bind to a narrow region near the site of initiation of transcription is of considerable inter est in terms of the mechanism of transcription of the rRNA gene.