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XB-ART-14710
Biochem J 1998 Jul 01;333 ( Pt 1):51-6. doi: 10.1042/bj3330051.
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The first high-mobility-group box of upstream binding factor assembles across-over DNA junction by basic residues.

Hu CH , Wang JM , Tseng HB .


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Upstream binding factor (UBF) is a eukaryotic RNA polymerase I-specific transcription factor. Its predominant DNA-binding motif, ubfHMG box 1, preserves DNA assembling activity that can bind two or more DNA duplexes simultaneously to form a crossover DNA junction. Here we investigate the basis of crossover DNA-assembling activity of ubfHMG box 1 by extensive mutagenesis analyses and mobility shift assay. Although the ubfHMG box 1 preserves a high mobility group (HMG) core structure, changing a number of the consensus hydrophobic and aromatic residues to alanine did not inhibit its crossover-assembling activity. This indicates that these residues do not directly participate in protein-DNA interaction. However, altering a series of basic residues in the helices 1 and 2 regions or the N-terminal extended strand of the ubfHMG box 1 motif had severe effects on DNA-assembling activity; however, certain non-specific DNA binding activity still remained. This suggests that the ubfHMG box 1 motif might extensively contact the backbone of a crossover junction through its multiple basic residues. Mutating a hydrophobic residue in the terminal dimerization domain inhibited the association of truncated Xenopus UBF, but had little effect on its crossover-assembling activity. This indicates that the UBF-crossover DNA complex is not established by the association of individual DNA-bound peptides.

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Species referenced: Xenopus
Genes referenced: ubtf

References [+] :
Bachvarov, The RNA polymerase I transcription factor xUBF contains 5 tandemly repeated HMG homology boxes. 1991, Pubmed, Xenbase