Dataset Information

Genome-wide analysis of the binding of the Hox protein Ultrabithorax and the Hox cofactor Homothorax in Drosophila

ABSTRACT: Hox genes encode a family of transcription factors that are key developmental regulators with a highly conserved role in specifying segmental diversity along the metazoan body axis. Although they have been shown to regulate a wide variety of downstream processes, direct transcriptional targets have been difficult to identify and this has been a major obstacle to our understanding of Hox gene function. Here we report the use of a YFP-tagged Drosophila protein-trap line together with chromatin immunoprecipitation and microarray analysis to identify genome-wide binding sites for the Hox protein Ultrabithorax (Ubx). We find 1,147 genes bound by Ubx in chromatin from the haltere imaginal disc, a prominent site of Ubx function where it specifies haltere versus wing development. The functional relevance of these genes is supported by their overlap with genes showing differential expression between wing and haltere imaginal discs. The Ubx-bound genes are highly enriched in genes involved in developmental processes. They contain both high-level regulatory genes as well as genes involved in more basic cell functions supporting the idea that Hox genes regulate many levels of developmental pathways. Several signalling pathways are highly enriched and within these pathways Ubx target genes occur at multiple level from ligands to transcriptional effectors. We also performed genome-wide analysis of the binding sites for the Hox cofactor Homothorax (Hth), revealing a striking similarity in the binding profiles of Hth and Ubx. We suggest that these binding profiles may be strongly influenced by chromatin accessibility and we provide evidence of a clear link between Ubx/Hth binding and the chromatin state at genes regulated by Polycomb silencing. The role of chromatin accessibility has important implications for Hox gene function and for genomic target selection by transcription factors in general.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE23864 | GEO | 2011/04/14

SECONDARY ACCESSION(S): PRJNA130505

REPOSITORIES: GEO

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Project description:Amongst the various different insect groups, there is remarkable diversity in the number and size of wings. However the development of the basic body plan in insects is similar to a large extent. The genes of the hox complex regulate various pathways to bring about the development or modification of different organs. Ubx, a gene of the bithorax hox complex is expressed in the third thoracic segment of insects and is known to specify the fate of wing appendage in that segment.To understand the role of Ubx and how its regulatory mechanism has evolved through the course of evolution we have compared its genome wide targets in different insect orders. The identification of regulatory pathways and the key players Ubx regulates is crucial to understand how it has controlled wing development across insect orders. Our lab has previously identified direct targets of Ubx in Drosophila using ChIP-chip (Agrawal et al, 2011). To further our knowledge on the role of regulation in development and modification of hind wing appendage we have studied the targets in the hind wings of other insects (silk moth; Lepidoptera and honeybee; Hymenoptera) and performed a comparative analysis. We have employed ChIP followed by illumina sequencing to identify the targets of Ubx in developing hind and fore wing buds of Bombyx larvae. This is a first next generation sequencing study in Lepidoptera in an attempt to understand wing development. Chromatin Immunoprecipitation (ChIP) was used to identify genome wide targets bound by Ubx in Bombyx larval wing buds. The experiment to enrich Ubx bound regions was carried out using a Bombyx N terminal-Ubx specific poylclonal antibody raised in Rabbit and purified against a Protein A column to obtain IgG fraction. An Immunoprecipitation (IP) with Normal Rabbit IgG was used as a negative control to eliminate the regions that pertained to non specific binding to an Immunogloubulin. The normalization of both ChIP and IgG was done against sequenced input chromatin. Two replicates of single end 36 bp reads were sequenced using Ilumina for all the three conditions and for both fore and hind wing tissue samples.The peaks common to both the replicates were considered after applying a FDR cutoff.The fore wing target set was used for comparison with the hind wing targets.

Dataset Information

Genome-wide analysis of the binding of the Hox protein Ultrabithorax and the Hox cofactor Homothorax in Drosophila

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