title: G4 DNA binding by LR1 and its subunits, nucleolin and hnRNP D, A role for G-G pairing in immunoglobulin switch recombination.
abstract: The immunoglobulin heavy chain switch regions contain multiple runs of guanines on the top (nontemplate) DNA strand. Here we show that LR1, a B cell-specific, duplex DNA binding factor, binds tightly and specifically to synthetic oligonucleotides containing G-G base pairs (KD </= 0.25 nM). LR1 also binds to single-stranded G-rich sequences (KD approximately 10 nM). The two subunits of LR1, nucleolin and hnRNP D, bind with high affinity to G4 DNA (KD = 0.4 and 0.5 nM, respectively). LR1 therefore contains two independent G4 DNA binding domains. We propose that LR1 binds with G-G-paired structures that form during the transcription of the S regions that is prerequisite to recombination in vivo. Interactions of donor and acceptor S regions with subunits of the LR1 could then juxtapose the switch regions for recombination.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Dempsey
authors.forename: H
authors.initials: H
authors.lastname: Sun
authors.forename: L A
authors.initials: LA
authors.lastname: Hanakahi
authors.forename: N
authors.initials: N
authors.lastname: Maizels
mesh_terms: D000906:Antibodies / Q000276:immunology; D001483:Base Sequence; D004247:DNA / Q000378:metabolism*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D007134:Immunoglobulin Switch Region / Q000235:genetics*; D010750:Phosphoproteins / Q000276:immunology / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D011995:Recombination, Genetic; D012261:Ribonucleoproteins / Q000276:immunology / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D000097796:Nucleolin
chemical_list: D000906:Antibodies; D004247:DNA; D017931:DNA Primers; D004268:DNA-Binding Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; D014157:Transcription Factors; D000097796:Nucleolin