TY - JOUR
T1 - Cooperative DNA binding by Xenopus transcription factor IIIA. Use of a 66-base pair DNA fragment containing the intragenic control region of the 5 S RNA gene to study specific and nonspecific interactions
AU - Daly, T. J.
AU - Wu, Cheng-Wen
PY - 1989/12/20
Y1 - 1989/12/20
N2 - The interaction of Xenopus transcription factor IIIA (TFIIIA) with a synthetic 66-base pair DNA fragment containing the intragenic control region (ICR) of the 5 S RNA gene was investigated by mobility shift gel electrophoresis and DNase I protection experiments. Specific EDTA-sensitive protein-DNA complexes were observed only in the presence of high concentrations of either the ICR-containing fragment or an excess of unlabeled nonspecific DNA. This predominant complex was determined to be composed of equal molar ratios of TFIIIA and in 66-base pair ICR-containing fragment, although complexes containing two TFIIIA molecules/ICR and three TFIIA molecules/ICR were also found. In the absence of excess unlabeled specific or nonspecific DNA, TFIIIA was observed to interact with the labeled 66-mer as an aggregate that remained at the top of the gel matrix. Although the binding affinities of TFIIIA for the 66-base pair specific DNA fragment and the 74-base pair nonspecific DNA fragment were comparable as observed by direct measurement with mobility shift gel electrophoresis, a greater than 500-fold difference was observed by competition experiments at high DNA concentrations. Furthermore, a similar difference was also detected when proteolytically cleaved TFIIIA was used in the binding reaction, which substantially reduced the protein-protein interactions. DNase I digestion patterns of the noncoding strand of the 66-mer in the absence or presence of TFIIIA demonstrated that this region of DNA is structurally equivalent to the ICR contained within the 5 S RNA gene. In addition, the mode of binding observed in the mobility shift gels is identical to that observed by direct footprint analysis. Protein-protein interactions appear, therefore, to be an intrinsic and necessary activity of TFIIIA.
AB - The interaction of Xenopus transcription factor IIIA (TFIIIA) with a synthetic 66-base pair DNA fragment containing the intragenic control region (ICR) of the 5 S RNA gene was investigated by mobility shift gel electrophoresis and DNase I protection experiments. Specific EDTA-sensitive protein-DNA complexes were observed only in the presence of high concentrations of either the ICR-containing fragment or an excess of unlabeled nonspecific DNA. This predominant complex was determined to be composed of equal molar ratios of TFIIIA and in 66-base pair ICR-containing fragment, although complexes containing two TFIIIA molecules/ICR and three TFIIA molecules/ICR were also found. In the absence of excess unlabeled specific or nonspecific DNA, TFIIIA was observed to interact with the labeled 66-mer as an aggregate that remained at the top of the gel matrix. Although the binding affinities of TFIIIA for the 66-base pair specific DNA fragment and the 74-base pair nonspecific DNA fragment were comparable as observed by direct measurement with mobility shift gel electrophoresis, a greater than 500-fold difference was observed by competition experiments at high DNA concentrations. Furthermore, a similar difference was also detected when proteolytically cleaved TFIIIA was used in the binding reaction, which substantially reduced the protein-protein interactions. DNase I digestion patterns of the noncoding strand of the 66-mer in the absence or presence of TFIIIA demonstrated that this region of DNA is structurally equivalent to the ICR contained within the 5 S RNA gene. In addition, the mode of binding observed in the mobility shift gels is identical to that observed by direct footprint analysis. Protein-protein interactions appear, therefore, to be an intrinsic and necessary activity of TFIIIA.
UR - http://www.scopus.com/inward/record.url?scp=0024351096&partnerID=8YFLogxK
U2 - 10.1016/S0021-9258(19)47075-0
DO - 10.1016/S0021-9258(19)47075-0
M3 - Article
C2 - 2584222
AN - SCOPUS:0024351096
VL - 264
SP - 20394
EP - 20402
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 34
ER -