TELOMERIC AND TETRAPLEX DNA-BINDING PROPERTIES OF QTBP42 - A HOMOLOG OF THE CARG BOX-BINDING PROTEIN CBF-A

qTBP42, a rat liver binding protein of telomeric and of guanine-rich s ingle stranded or tetraplex DNA (Sarig, G., Weisman-Shomer, P., Erlitz ki, R., and Fry, M. (1997) J. Biol. Chem. 272, 4474-4482), is identifi ed here by its partial amino acid sequence as a homologue of the mouse muscle cell CArG box binding protein CBF-A. Complexes of qTBP42 with single stranded telomeric DNA or with double or single stranded CArG; DNA are formed non-cooperatively and have a similar nanomolar-range di ssociation constants, K-d. Double stranded telomeric or Plasmid DNA or poly cl[(I-C)] are bound by qTBP42 less tightly. Analysis of the bind ing of tetramolecular quadruplex structures of the IgG switch sequence indicates that one molecule of qTBP42 associates with a single cluste r of guanine quartets. The tight binding by qTBP42 of CArG box DNA, te lomeric DNA and quadruplex DNA suggests that this protein may bind mul tiple targets in cellular DNA. (C) 1997 Academic Press.