PROTEIN-BINDING TO REITERATED MOTIFS WITHIN THE WHEAT RIBOSOMAL-RNA GENE PROMOTER AND UPSTREAM REPEATS

The binding of specific proteins in wheat nuclear extracts to the -34 to +10 region of the wheat ribosomal RNA gene promoter has been detected. DNase I footprinting revealed two binding regions, one spanning the transcription initiation site from -7 to +2, and a larger one further upstream from around -29 to -15. An oligonucleotide made to the -30 to -14 promoter region binds a protein in a sequence-specific manner. This protein also binds specifically to sites with related sequences further upstream in the promoter and in the associated intergenic spacer repeats. A consensus sequence, CATGG--GCAAAAC, was defined from the different binding sites of the protein. These results, taken together with in vivo results on the enhanced activity of nucleoli containing ribosomal RNA genes with more intergenic spacer repeats, endorse the hypothesis that ribosomal RNA gene transcription is regulated by the extent of binding of a protein to many sites upstream of the transcriptional start site.