The BEN Domain Protein Insensitive Binds to the Fab-7 Chromatin Boundary To Establish Proper Segmental Identity in Drosophila

Genetics. 2018 Oct;210(2):573-585. doi: 10.1534/genetics.118.301259. Epub 2018 Aug 6.

Abstract

Boundaries (insulators) in the Drosophila bithorax complex (BX-C) delimit autonomous regulatory domains that orchestrate the parasegment (PS)-specific expression of the BX-C homeotic genes. The Fab-7 boundary separates the iab-6 and iab-7 regulatory domains, which control Abd-B expression in PS11 and PS12, respectively. This boundary is composed of multiple functionally redundant elements and has two key functions: it blocks cross talk between iab-6 and iab-7 and facilitates boundary bypass. Here, we show that two BEN domain protein complexes, Insensitive and Elba, bind to multiple sequences located in the Fab-7 nuclease hypersensitive regions. Two of these sequences are recognized by both Insv and Elba and correspond to a CCAATTGG palindrome. Elba also binds to a related CCAATAAG sequence, while Insv does not. However, the third Insv recognition sequences is ∼100 bp in length and contains the CCAATAAG sequence at one end. Both Insv and Elba are assembled into large complexes (∼420 and ∼265-290 kDa, respectively) in nuclear extracts. Using a sensitized genetic background, we show that the Insv protein is required for Fab-7 boundary function and that PS11 identity is not properly established in insv mutants. This is the first demonstration that a BEN domain protein is important for the functioning of an endogenous fly boundary.

Keywords: Abdominal B; BEN DNA-binding domain; Elba; Fab-7; Insensitive; bithorax; boundary; chromatin; insulator; parasegment identity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Co-Repressor Proteins / genetics
  • Co-Repressor Proteins / metabolism*
  • Drosophila
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Embryonic Development / genetics
  • Gene Expression Regulation, Developmental*
  • Insulator Elements*
  • Protein Binding
  • Transcription Factors / genetics
  • Transcription Factors / metabolism

Substances

  • Bsg25A protein, Drosophila
  • Co-Repressor Proteins
  • Drosophila Proteins
  • Elba2 protein, Drosophila
  • Insv protein, Drosophila
  • Transcription Factors

Associated data

  • figshare/10.6084/m9.figshare.6932915