科研之友
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摘要
We have used electrophoretic mobility shift assays (EMSA) to detect B cell lineage-specific nuclear proteins that bind to diverse segments within and 3' of the Ig H chain gene cluster. DNA binding sites include sequences 5' of each of the following C region genes: mu, gamma-1, gamma-2a, epsilon and alpha. For the most part, these binding sites lie 5' of C(H)-associated tandem repeats. Binding sites for the same B cell lineage-specific proteins have also been defined in the region 3' of C-alpha, close to a recently described B cell-specific enhancer element. Cross-competition of EMSA indicates that the B cell lineage-specific nucleoprotein is indistinguishable from those described previously by others: S-alpha-BP and BSAP. Because of the diverse sequences recognized by this protein, we term it NF-HB, B-lineage-specific nuclear factor that binds to Ig H gene segments. EMSA using segments 5' of S-gamma-2a (5'S-gamma-2a-176) and 3' of C-alpha (3'-alpha-88) shows multiple binding complexes, two of which are B cell lineage specific. The B cell-specific complex with fastest mobility contains only NF-HB, and the one with slowest mobility contains NF-HB together with a ubiquitous DNA-binding protein(s). The ubiquitous binding protein is different for 5' S-gamma-2a- 176 and for 3'alpha-88, representing the formation of protein-NF-HB complexes specific for these particular Ig DNA regions. Spleen cells show a single band upon EMSA with either 5'S-gamma-2a-176 or 3'alpha-88. Upon LPS stimulation, additional binding complexes of slower mobility were formed resulting in a pattern comparable to those detected in pro-B, pre-B, and B cell lines. We hypothesize that NF-HB may promote physical interactions between the 3'alpha-enhancer and segments of the Ig H gene cluster.
- 出版日期1992-5-1
