title: Species-specific rDNA transcription is due to promoter-specific binding factors.
abstract: RNA polymerase I transcription factors were purified from HeLa and mouse L cell extracts by phosphocellulose chromatography. Three fractions from each species were found to be required for transcription. One of these fractions, virtually devoid of RNA polymerase I activity, was found to form a stable preinitiation complex with small DNA fragments containing promoter sequences from the homologous but not the heterologous species. These species-specific DNA-binding factors can explain nucleolar dominance in vivo in mouse-human hybrid somatic cells and species specificity in cell-free, RNA polymerase I-dependent transcription systems. The evolution of species-specific transcriptional control signals may be the natural outcome of a special relationship that exists between the RNA polymerase I transcription machinery and the multigene family coding for rRNA.
mesh_terms: D000818:Animals; D004247:DNA / Q000378:metabolism*; D004275:DNA, Ribosomal; D006367:HeLa Cells; D006801:Humans; D006822:Hybrid Cells / Q000378:metabolism; D007739:L Cells; D051379:Mice; D009876:Operon; D012318:RNA Polymerase I / Q000378:metabolism; D013045:Species Specificity; D013698:Templates, Genetic; D014158:Transcription, Genetic
chemical_list: D004275:DNA, Ribosomal; D004247:DNA; D012318:RNA Polymerase I