TY - JOUR
T1 - Concerted repression of an immunoglobulin heavy-chain enhancer, 3′ αE(hs1,2)
AU - Singh, Mallika
AU - Birshtein, Barbara K.
PY - 1996/4/30
Y1 - 1996/4/30
N2 - The transcription factor, B-cell-specific activator protein (BSAP), represses the murine immunoglobulin heavy-chain 3′ enhancer 3′ αE(hs1,2) in B cells. Analysis of various 3′ αE deletional constructs indicates that sequences flanking a and b BSAP-binding sites are essential for appropriate regulation of the enhancer. An octamer motif 5′ of the a site and a specific G-rich motif 3′ of the b site were identified by competition in electrophoretic mobility-shift assays and methylation-interference foot-printing analysis. Site-directed mutagenesis of either the octamer or G-rich sites resulted in the complete release of repression of 3′ αE(hs1,2), implicating these two motifs in the repression of this enhancer in B cells. However, when both BSAP-binding sites were mutated, the octamer and G-rich motifs functioned as activators. Moreover, in plasma cells, when BSAP is not expressed, 3′ aE(hs1,2) is active, and its activity depends on the presence of the other two factors. These results suggest that in B cells, 3′ αE(hs1,2) is down-regulated by the concerted actions of BSAP, octamer, and G-rich DNA-binding proteins. Supporting this notion of concerted repression, a physical interaction between BSAP and octamer-binding proteins was demonstrated using glutathione S-transferase fusion proteins. Thus, concerted repression of 3′ αE(hs1,2) in B cells provides a sensitive mechanism by which this enhancer, either individually or as part of a locus-controlling region, is highly responsive to any of several participating factors.
AB - The transcription factor, B-cell-specific activator protein (BSAP), represses the murine immunoglobulin heavy-chain 3′ enhancer 3′ αE(hs1,2) in B cells. Analysis of various 3′ αE deletional constructs indicates that sequences flanking a and b BSAP-binding sites are essential for appropriate regulation of the enhancer. An octamer motif 5′ of the a site and a specific G-rich motif 3′ of the b site were identified by competition in electrophoretic mobility-shift assays and methylation-interference foot-printing analysis. Site-directed mutagenesis of either the octamer or G-rich sites resulted in the complete release of repression of 3′ αE(hs1,2), implicating these two motifs in the repression of this enhancer in B cells. However, when both BSAP-binding sites were mutated, the octamer and G-rich motifs functioned as activators. Moreover, in plasma cells, when BSAP is not expressed, 3′ aE(hs1,2) is active, and its activity depends on the presence of the other two factors. These results suggest that in B cells, 3′ αE(hs1,2) is down-regulated by the concerted actions of BSAP, octamer, and G-rich DNA-binding proteins. Supporting this notion of concerted repression, a physical interaction between BSAP and octamer-binding proteins was demonstrated using glutathione S-transferase fusion proteins. Thus, concerted repression of 3′ αE(hs1,2) in B cells provides a sensitive mechanism by which this enhancer, either individually or as part of a locus-controlling region, is highly responsive to any of several participating factors.
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U2 - 10.1073/pnas.93.9.4392
DO - 10.1073/pnas.93.9.4392
M3 - Article
C2 - 8633077
AN - SCOPUS:0029989292
SN - 0027-8424
VL - 93
SP - 4392
EP - 4397
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 9
ER -