EBP-80, a transcription factor closely resembling the human autoantigen Ku, recognizes single- to double-strand transitions in DNA

M. Falzon, J. W. Fewell, E. L. Kuff

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202 Scopus citations


We have previously reported the purification and characterization of the transcription factor EBP-80 (Falzon, M., and Kuff, E. L. (1989) J. Biol. Chem. 264, 21915-21922). EBP-80 mediates the DNA methylation effect on transcription from an endogenous proviral long terminal repeat. Here we show that EBP-80 is very similar if not identical to the Ku autoantigen, a heterodimeric nuclear protein first detected by antibodies from autoimmune patients (Mimori, T., Akizuki, M., Yamagata, H., Inada, S., Yoshida, S., and Homma, M. (1981) J. Clin. Invest. 68, 611-620). A number of laboratories have shown that the Ku protein complex binds to free double-stranded DNA ends. In this study, we have examined the binding properties of EBP-80. EBP-80 binds single-stranded DNA with low affinity. Binding to random sequence double- stranded DNA depends on the length of the duplex and is optimal with oligomers of 30 and 32 base pairs; the protein complexes formed with these oligomers have K(d) values of 15-20 pM. It binds with comparable high affinities to blunt-ended duplex DNA, to duplex DNA ending in hairpin loops, and to constructs in which an internal segment of duplex DNA is flanked by single-strand extensions. EBP-80 also interacts effectively with circular duplex molecules containing a 30-nucleotide single-stranded region (gap) or a double-stranded segment of nonhomology (bubble), but only weakly with the corresponding closed circular construct made up entirely of duplex DNA. EBP- 80 prefers A/T to G/C ends. The binding properties of EBP-80 are consistent with the hypothesis that it recognizes single- to double-strand transitions in DNA. A model is presented for the interaction of EBP-80 with its target sequence in the proviral long terminal repeat.

Original languageEnglish (US)
Pages (from-to)10546-10552
Number of pages7
JournalJournal of Biological Chemistry
Issue number14
StatePublished - Jan 1 1993


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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