title: Z-DNA-binding proteins. Identification critically depends on the proper choice of ligands.
abstract: We have previously isolated from bull testis three proteins of molecular mass 31, 33, and 58 kDa that we have tentatively characterized as high affinity Z-DNA-binding proteins. This inference was based on their preferential binding to brominated poly(dG-dC).poly(dG-dC) in Z-form as opposed to the unbrominated polynucleotide in B-form (Gut, S. H., Bischoff, M., Hobi, R., and Kuenzle, C. C. (1987) Nucleic Acids Res. 15, 9691-9705). By partial amino acid sequencing we have provisionally identified the 31- and 33-kDa proteins as members of the high mobility group 2 and 1 protein families, respectively, whereas the 58-kDa protein has so far remained unidentified (Christen, Th., Bischoff, M., Hobi, R., and Kuenzle, C. C. (1990) FEBS Lett. 267, 139-141). In the present study, we have critically reassessed the binding specificity of these three proteins by using more natural Z- and B-DNA ligands. As such we chose supercoiled and relaxed DNA minicircles containing a d(CG)7 insert in the Z- and B-conformation, respectively. Filter binding tests and gel retardation assays performed with these ligands showed that the three testis proteins either do not discriminate between Z- and B-DNA (31- and 33-kDa proteins) or even have a preference for B-DNA (58-kDa protein). Therefore, we question the validity of using brominated poly(dG-dC).poly(dG-dC) as an indicator of Z-DNA binding.
authors.affiliation: Institut für Pharmakologie und Biochemie, Universität Zürich-Irchel, Switzerland.
authors.forename: K J
authors.initials: KJ
authors.lastname: Rohner
authors.forename: R
authors.initials: R
authors.lastname: Hobi
authors.forename: C C
authors.initials: CC
authors.lastname: Kuenzle
mesh_terms: D000818:Animals; D000906:Antibodies; D001483:Base Sequence; D002417:Cattle; D004247:DNA / Q000378:metabolism*; D004270:DNA, Circular / Q000378:metabolism; D018105:DNA, Kinetoplast; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000378:metabolism; D013737:Testis / Q000378:metabolism*
chemical_list: D000906:Antibodies; D004270:DNA, Circular; D018105:DNA, Kinetoplast; D004268:DNA-Binding Proteins; D011089:Polydeoxyribonucleotides; C019530:poly(dC-dG); D004247:DNA