Mcp and Fab-7: Molecular analysis of putative boundaries of cis-regulatory domains in the bithorax complex of Drosophila melanogaster

François Karch, Mireille Galloni, Làszlò Sipos, Janos Gausz, Henrik Gyurkovics, Paul Sched

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A very large cis-regulatory region of -300 kb is responsible for the complex patterns of expression of the three homeotic genes of the bithorax complex Ubx, abd-A and Abd-B. This region can be subdivided in nine parasegment-specific regulatory subunits. Recent genetic and molecular analysis has revealed the existence of two novel cis-regulatory elements Mcp and Fab-7. Mcp is located between iab-4 and iab-5, the parasegment-specific regulatory subunits which direct Abd-B in parasegments 9 and 10. Similarly, Fab-7 is located between iab-6 and iab-7, the parasegment 11 and 12-specific regulatory units. Mcp and Fab-7 appear to function as domain boundaries that separate adjacent cis-regulatory units. We report the analysis of two new Mcp mutant deletions (Mcp27 and Mcp8116) that allow us to localize sequences essential for boundary function to a - 0 .4 kb DNA segment. These essential sequences closely coincide to a -0.3 kb nuclease hypersensitive region in chromatin. We also show that sequences contributing to the Fab-7 boundary appear to be spread over a larger stretch of DNA, but like Mcp have an unusual chromatin structure.

Original languageEnglish
Pages (from-to)3138-3146
Number of pages9
JournalNucleic acids research
Issue number15
Publication statusPublished - Aug 11 1994


ASJC Scopus subject areas

  • Genetics

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