Fab-7 functions as a chromatin domain boundary to ensure proper segment specification by the Drosophila bithorax complex

Kirsten Hagstrom, Martin Muller, Paul Daniel Schedl

Research output: Contribution to journalArticlepeer-review

196 Scopus citations

Abstract

Fab-7 deletions in the bithorax complex have a novel gain-of-function phenotype, typically transforming parasegment 11 (PS11) into PS12 identity. Genetic analysis indicates that removal of the Fab-7 element results in the fusion of the iab-6 (PS11) and iab-7 (PS12) cis-regulatory domains into a single regulatory domain that inappropriately regulates Abdominal-B in PS11. This has led to the hypothesis that Fab-7 is a chromatin domain boundary that normally functions to ensure the autonomous activity of the iab-6 and iab-7 cis-regulatory domains. We use several different enhancer blocking assays to demonstrate that Fab-7 has the insulating properties expected of a domain boundary. We define a minimal fragment of Fab-7 sufficient for enhancer blocking, and demonstrate that it is completely distinct from an adjacent Polycomb-dependent silencer. We compare Fab-7 to the su(Hw) insulator element, and show that Fab-7 enhancer blocking activity is intermediate between that of five and twelve reiterated binding sites for the Su(Hw) protein. These results support the model that Fab-7 functions as a domain boundary within the context of the bithorax complex, making Fab-7 one of the first boundary elements that is known to have an essential function in vivo.

Original languageEnglish (US)
Pages (from-to)3202-3215
Number of pages14
JournalGenes and Development
Volume10
Issue number24
DOIs
StatePublished - Dec 15 1996

All Science Journal Classification (ASJC) codes

  • Genetics
  • Developmental Biology

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