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Mol. Cell. Biol., 08 1996, 4544-4554, Vol 16, No. 8
BS Nikolajczyk, B Nelsen and R Sen
The lymphocyte-specific immunoglobulin mu heavy-chain gene intronic
enhancer is regulated by multiple nuclear factors. The previously defined
minimal enhancer containing the muA, muE3, and muB sites is transactivated
by a combination of the ETS-domain proteins PU.1 and Ets- 1 in nonlymphoid
cells. The core GGAAs of the muA and muB sites are separated by 30
nucleotides, suggesting that ETS proteins bind to these sites from these
same side of the DNA helix. We tested the necessity for appropriate spatial
alignment of these elements by using mutated enhancers with altered
spacings. A 4- or 10-bp insertion between muE3 and muB inactivated the mu
enhancer in S194 plasma cells but did not affect in vitro binding of Ets-1,
PU.1, or the muE3-binding protein TFE3, alone or in pairwise combinations.
Circular permutation and phasing analyses demonstrated that PU.1 binding
but not TFE3 or Ets-1 bends mu enhancer DNA toward the major groove. We
propose that the requirement for precise spacing of the muA and muB
elements is due in part to a directed DNA bend induced by PU.1.
Copyright © 1996, American Society for Microbiology
Precise alignment of sites required for mu enhancer activation in B cells
Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts 02254-9110, USA.
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