title: Properties of B cell stage specific and ubiquitous nuclear factors binding to immunoglobulin heavy chain gene switch regions.
abstract: The Ig heavy chain (IgH) constant region (CH) class switch is manifested by DNA deletions which exchange the C mu gene of a functional VDJ-CH rearrangement for a C gamma, C epsilon or C alpha gene. Repetitive sequences (S regions) 5' of each CH gene mediate CH gene switch recombination by an illegitimate mechanism. S mu can be subdivided into S mu 5' (non-repetitive) and S mu 3' (repetitive) components with recombination occurring in either part. Here, we describe the properties of ubiquitous and B cell stage specific S mu binding factors NFS mu-U1 and NFS mu-B1 respectively. U1 only bound to S mu 5' sequences, and B1 to S mu 5', S mu 3' sequences and to other S regions with varying affinities. DMS and OP-Cu footprinting revealed the sequence AAAAAGCATGGCTGA in the U1 site while the B1 S mu 5' site overlapped the 3' end of the U1 binding site and also contained additional 3' flanking S mu repeat motifs (GAGCTGAGATGGGTGGGCT). Binding site competition assays reveal that NFS mu-B1 is either very related or identical to S alpha BP (described by Waters et al., Mol. Cell Biol. 9:5594, 1989) and BSAP (identified by Barberis et al., Genes Devl. 4:849, 1990) which were shown to bind to two sequences upstream of the S alpha repeats and within the promoters of sea urchin histone genes respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Molecular and Cellular Biology, SUNY, Stony Brook 11794-5215.
authors.forename: L
authors.initials: L
authors.lastname: Xu
authors.forename: M G
authors.initials: MG
authors.lastname: Kim
authors.forename: K B
authors.initials: KB
authors.lastname: Marcu
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology*; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005803:Genes, Immunoglobulin; D005812:Genes, Switch; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D011995:Recombination, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D016415:Sequence Alignment; D013696:Temperature
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins