A purified transcription factor (TIF-IB) binds to essential sequences of the mouse rDNA promoter.
A transcription factor that is specific for mouse rDNA has been partially purified from Ehrlich ascites cells. This factor [designated transcription initiation factor (TIF)-IB] is required for accurate in vitro synthesis of mouse rRNA in addition to RNA polymerase I and another regulatory factor, TIF-IA. TIF-IB activity is present in extracts both from growing and nongrowing cells in comparable amounts. Prebinding competition experiments with wild-type and mutant templates suggest that TIF-IB interacts with the core control element of the rDNA promoter, which is located immediately upstream of the initiation site. The specific binding of TIF-IB to the RNA polymerase I promoter is demonstrated by exonuclease III protection experiments. The 3' border of the sequences protected by TIF-IB is shown to be on the coding strand at position -21 and on the noncoding strand at position -7. The results suggest that direct binding of TIF-IB to sequences in the core promoter element is the mechanism by which this factor imparts promoter selectivity to RNA polymerase I.
Clos
J
J
Buttgereit
D
D
Grummt
I
I
D000818:Animals; D001483:Base Sequence; D004275:DNA, Ribosomal / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D011401:Promoter Regions, Genetic; D012318:RNA Polymerase I / Q000378:metabolism; D013698:Templates, Genetic; D014157:Transcription Factors / Q000302:isolation & purification
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D014157:Transcription Factors; D012318:RNA Polymerase I