Int Immunol 1992 Aug 01;48:875-87. doi: 10.1093/intimm/4.8.875.

Properties of B cell stage specific and ubiquitous nuclear factors binding to immunoglobulin heavy chain gene switch regions.

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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)

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Genes referenced: LOC100887844 LOC115919910