A survey of protein-DNA interaction sites within the murine immunoglobulin heavy chain locus reveals a particularly complex pattern around the DQ52 element.
The expression of immunoglobulin (Ig) genes is regulated at two levels: rearrangement of individual gene segments and transcription of continuous genes. To find transacting factors involved in mediating locus- and segment specific gene activation and expression, we surveyed a 3600-bp genomic region of the murine Ig heavy chain locus, spanning from the DQ52 element to the Ig heavy chain intron enhancer. We discovered nine, previously undescribed, protein-DNA complexes and estimated their individual binding-affinity preferences (Kr) by quantitative gel shift measurements. We observed one novel protein DNA interaction at the enhancer, two in the JH1 region and six within a 300-bp region immediately 5' to the DQ52 locus. The latter show a complex and specific binding pattern when comparing nuclear extracts derived from pre-B cells and fibroblasts. Further characterization of the interactions at the DQ52 locus by electron microscopy revealed the preferential formation of a protein complex binding to the DQ52 locus with pre B cell extracts. This behavior and the clustering of interaction sites 5' to the DQ52 element suggest that this region is involved in the regulation of heavy chain gene assembly.
Kottmann
A H
AH
Max-Planck Institut für Immunobiologie, Freiburg, FRG.
Brack
C
C
Eibel
H
H
Köhler
G
G
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002874:Chromosome Mapping; D004247:DNA / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005803:Genes, Immunoglobulin; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D051379:Mice; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D011506:Proteins / Q000378:metabolism*
D007143:Immunoglobulin Heavy Chains; D011506:Proteins; D004247:DNA