The human protein translin specifically binds single-stranded microsatellite repeats, d(GT)n, and G-strand telomeric repeats, d(TTAGGG)n: a study of the binding parameters.
We have previously identified in human fibroblasts a multisubunit protein (designated PGB) that specifically bound single-stranded G-rich microsatellite DNA sequences. PGB was later found to be identical, or closely related to translin, an octameric protein that bound single-stranded DNA consisting of sequences flanking chromosomal translocations. Here, we report that recombinant translin binds single-stranded microsatellite repeats, d(GT)n, and G-strand telomeric repeats, d(TTAGGG)n, with higher affinities (Kdis approximately = 2 nM and Kdis approximately = 12.5 nM, respectively, in 100 mM NaCl and 25 degrees C) than the affinity with which it binds a prototypical sequence flanking translocation sites (Kdis approximately = 23 nM). Translin also binds d(GT)n and d(TTAGGG)n overhangs linked to double-stranded DNA with equilibrium constants in the nanomolar range. Formation of DNA quadruplexes by the d(TTAGGG)n repeats inhibits their binding to translin. A further study of the binding parameters revealed that the minimal length of d(GT)n and d(TTAGGG)n oligonucleotides that a translin octamer can bind is 11 nucleotides, but that such oligonucleotides containing up to 30 nucleotides can bind only a single translin octamer. However, the oligonucleotides d(GT)27 and d(TTAGGG)9 bind two octamers with negative cooperativity. Translin does not detectably bind single-stranded d(GT)n sequences embedded within double-stranded DNA. Based on our data, we propose that translin might be involved in the control of recombination at d(GT)n.d(AC)n microsatellites and in telomere maintenance.
Jacob
Eyal
E
Department of Biology, Technion-Israel Institute of Technology, Haifa 32,000, Israel.
Pucshansky
Lev
L
Zeruya
Eleanor
E
Baran
Nava
N
Manor
Haim
H
D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D018895:Microsatellite Repeats / Q000235:genetics*; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D016615:Telomere / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D011994:Recombinant Proteins; C095563:TSN protein, human