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Genetics. 2017 Feb;205(2):589-603. doi: 10.1534/genetics.116.195586. Epub 2016 Dec 22.

Different Evolutionary Strategies To Conserve Chromatin Boundary Function in the Bithorax Complex.

Author information

1
Department of Genetics and Evolution, University of Geneva, Geneva 4, Switzerland.
2
Department of Molecular Biology, Princeton University, New Jersey 08544.
3
Lewis-Sigler Institute for Integrative Genomics, Princeton University, New Jersey 08544.
4
Department of Evolution and Ecology, Princeton University, New Jersey 08544.
5
Department of Molecular Biology, Princeton University, New Jersey 08544 pschedl@princeton.edu.

Abstract

Chromatin boundary elements subdivide chromosomes in multicellular organisms into physically independent domains. In addition to this architectural function, these elements also play a critical role in gene regulation. Here we investigated the evolution of a Drosophila Bithorax complex boundary element called Fab-7, which is required for the proper parasegment specific expression of the homeotic Abd-B gene. Using a "gene" replacement strategy, we show that Fab-7 boundaries from two closely related species, D. erecta and D. yakuba, and a more distant species, D. pseudoobscura, are able to substitute for the melanogaster boundary. Consistent with this functional conservation, the two known Fab-7 boundary factors, Elba and LBC, have recognition sequences in the boundaries from all species. However, the strategies used for maintaining binding and function in the face of sequence divergence is different. The first is conventional, and depends upon conservation of the 8 bp Elba recognition sequence. The second is unconventional, and takes advantage of the unusually large and flexible sequence recognition properties of the LBC boundary factor, and the deployment of multiple LBC recognition elements in each boundary. In the former case, binding is lost when the recognition sequence is altered. In the latter case, sequence divergence is accompanied by changes in the number, relative affinity, and location of the LBC recognition elements.

KEYWORDS:

DNA binding proteins; boundary element; conservation of function; evolution; insulator

PMID:
28007886
PMCID:
PMC5289839
DOI:
10.1534/genetics.116.195586
[Indexed for MEDLINE]
Free PMC Article

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