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Abstract <p>Boundary elements in the <i>Drosophila</i> Bithorax complex partition the <i>Abd-B</i> regulatory landscape into autonomous domains that require insulation and boundary bypass. We surveyed Large Boundary Complex (LBC) occupancy across <i>Abd-B</i> boundaries and detected binding at <i>Fab-7</i> and <i>Fab-8</i>, but not at <i>Fab-6</i> or at <i>Mcp</i> (the boundary between <i>Abd-B</i> and <i>abd-A</i>). Despite lacking LBC binding, <i>Fab-6</i> supports boundary bypass, demonstrating that bypass can occur without LBC. <i>Fab-7</i> and <i>Fab-8</i> share two conserved motifs (“green” and “blue”); however, mutational analysis shows that neither motif is required for LBC recruitment. These findings reveal selective, context-dependent LBC occupancy at <i>Abd-B</i> boundaries and imply that additional factor(s) and/or higher-order sequence organization underlie bypass activity. Thus, LBC is not universally required for boundary bypass, and its recruitment to <i>Fab-7</i>/<i>8</i> is independent of the shared “green/blue” motifs.</p>

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The Late Boundary Complex (LBC) Selectively Binds the Fab-7/Fab-8 Boundaries, but not Fab-6 or Mcp, in the Abd-B Regulatory Region of Drosophila melanogaster

  • 期刊论文

  • 发表日期：

    2026年2月1日

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  • A. N. Ibragimov,
  • O. V. Kyrchanova,
  • P. G. Georgiev,
  • P. Schedl

摘要

Abstract

Boundary elements in the Drosophila Bithorax complex partition the Abd-B regulatory landscape into autonomous domains that require insulation and boundary bypass. We surveyed Large Boundary Complex (LBC) occupancy across Abd-B boundaries and detected binding at Fab-7 and Fab-8, but not at Fab-6 or at Mcp (the boundary between Abd-B and abd-A). Despite lacking LBC binding, Fab-6 supports boundary bypass, demonstrating that bypass can occur without LBC. Fab-7 and Fab-8 share two conserved motifs (“green” and “blue”); however, mutational analysis shows that neither motif is required for LBC recruitment. These findings reveal selective, context-dependent LBC occupancy at Abd-B boundaries and imply that additional factor(s) and/or higher-order sequence organization underlie bypass activity. Thus, LBC is not universally required for boundary bypass, and its recruitment to Fab-7/8 is independent of the shared “green/blue” motifs.