Unknown,Transcriptomics,Genomics,Proteomics

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Impacts of the Ubiquitous Factor Zelda on Bicoid-dependent DNA-binding and Transcription in Drosophila

ABSTRACT: In vivo crosslinking studies suggest that the Drosophila transcription factor Bicoid (Bcd) binds to several thousand sites during early embryogenesis, but it is not clear how many of these binding events are functionally important. In contrast, reporter gene studies have identified more than 60 Bcd-dependent enhancers, all of which contain clusters of the consensus binding sequence TAATCC. These studies also identified clusters of TAATCC motifs (inactive fragments) that failed to drive Bcd-dependent activation. In general, active fragments showed higher levels of Bcd-binding in vivo, and were enriched in predicted binding sites for the ubiquitous maternal protein Zelda (Zld). Here we test the role of Zld in Bcd-mediated binding and transcription. Removal of Zld function and mutations in Zld sites caused significant reductions in Bcd-binding to known enhancers, and variable effects on the activation and spatial positioning of Bcd-dependent expression patterns. Genome-wide binding experiments in Zld mutants showed variable effects on Bcd-binding peaks, ranging from strong reductions to significantly enhanced levels of binding. Increases in Bcd binding caused the precocious Bcd-dependent activation of genes that are normally not expressed in early embryos, suggesting that Zld controls the genome-wide binding profile of Bcd at the qualitative level, and is critical for selecting target genes for activation in the early embryo. These results underscore the importance of combinatorial binding in enhancer function, and provide data that will help predict regulatory activities based on DNA sequence. 1-3 hour wild type and zelda mutant embryos were examined for Bicoid binding using Illumina HiSeq 2000. The Bcd antibody is a rabbit polyclonal antiserum raised against full length Drosophila Bcd protein (Ochoa-Espinosa et al. 2009 PNAS). The antiserum was further purified using the Protein A Antibody Purification Kit (Sigma) for ChIP-seq.

ORGANISM(S): Drosophila melanogaster

SUBMITTER: Stephen Small

PROVIDER: E-GEOD-55256 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Impacts of the ubiquitous factor Zelda on Bicoid-dependent DNA binding and transcription in Drosophila.

Xu Zhe Z Chen Hongtao H Ling Jia J Yu Danyang D Struffi Paolo P Small Stephen S

Genes & development 20140301 6

In vivo cross-linking studies suggest that the Drosophila transcription factor Bicoid (Bcd) binds to several thousand sites during early embryogenesis, but it is not clear how many of these binding events are functionally important. In contrast, reporter gene studies have identified >60 Bcd-dependent enhancers, all of which contain clusters of the consensus binding sequence TAATCC. These studies also identified clusters of TAATCC motifs (inactive fragments) that failed to drive Bcd-dependent act ...[more]

PMID: 24637116

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Project description:The earliest stages of development in most metazoans are driven by maternally deposited proteins and mRNAs, with widespread transcriptional activation of the zygotic genome occurring hours after fertilization, at a period known as the maternal-to-zygotic transition (MZT). In Drosophila, the MZT is preceded by the transcription of a small number of genes that initiate sex determination, patterning and other essential developmental processes. The zinc-finger transcription factor Zelda (ZLD) plays a key role in the transcriptional activation of these earliest-expressed genes. To better understand the mechanisms of ZLD activation and the range of its targets, we used chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-Seq) to map regions bound by ZLD prior to (mitotic cycles 8 and 9), during (mitotic cycles 13 and early 14) and after (late mitotic cycle 14) the MZT. Although only a handful of genes are transcribed prior to mitotic cycle 10, we identified thousands of regions bound by ZLD in cycle 8-9 embryos, most of which remain bound through mitotic cycle 14. As expected, these ZLD-bound regions include the promoters and enhancers of the small subset of genes transcribed at this early stage. However we also observed ZLD bound at cycle 8-9 to the promoters of a large fraction of the several thousand genes whose first transcription does not occur until roughly an hour and four mitotic cycles later. These early ZLD-bound regions include virtually all of the thousands of known and presumed enhancers bound at cycle 14 by the transcription factors that regulate patterned gene activation during the MZT. The association between early ZLD binding and MZT activity is so strong that ZLD binding alone can be used to identify active promoters and regulatory sequences with high specificity and selectivity. This strong early association of ZLD with regions not active until the MZT suggests that ZLD is not only required for the earliest wave of transcription, but also plays a major role in activating the genome at the MZT. Genome-wide mapping of Zelda in wild-type Drosophila melanogaster embryos prior (mitotic cycles 8-9), during (cycles 13-14), and after (late cycle 14) maternal-to-zygotic transition

Dataset Information

Impacts of the Ubiquitous Factor Zelda on Bicoid-dependent DNA-binding and Transcription in Drosophila

Publications

Impacts of the ubiquitous factor Zelda on Bicoid-dependent DNA binding and transcription in Drosophila.

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