Telomeric and Tetraplex DNA Binding Properties ofqTBP42:A Homologue of the CArG Box Binding Protein CBF-A

Abstract

qTBP42,a rat liver binding protein of telomeric and of guanine-rich single stranded or tetraplex DNA (Sarig, G., Weisman-Shomer, P., Erlitzki, R., and Fry, M. (1997)J. Biol. Chem.272, 4474-4482), is identified here by its partial amino acid sequence as a homologue of the mouse muscle cell CArG box binding protein CBF-A. Complexes ofqTBP42with single stranded telomeric DNA or with double or single stranded CArG DNA are formed non-cooperatively and have a similar nanomolar-range dissociation constants, Kd. Double stranded telomeric or Plasmid DNA or poly d[(I-C)] are bound byqTBP42less tightly. Analysis of the binding of tetramolecular quadruplex structures of the IgG switch sequence indicates that one molecule ofqTBP42associates with a single cluster of guanine quartets. The tight binding byqTBP42of CArG box DNA, telomeric DNA and quadruplex DNA suggests that this protein may bind multiple targets in cellular DNA.