Project description:Background: Insulators are the multifunctional DNA binding proteins that perform architectural functions and regulate gene transcription. Although insulators have a well-established role in genome organization, it is still unclear how insulator proteins affect the control of tissue-specific processes. Drosophila insulator BEAF32 (Boundary Element-Associated Factor of 32 kD) is a component of chromatin complexes found in the open chromatin regions containing promoters of housekeeping genes. BEAF32 knockout impairs oogenesis and female fertility suggesting its specific functions during oogenesis Results: To get a better understanding of BEAF32 roles in oogenesis, we first examined its ovarian binding targets and discovered an enrichment of its localization sites in the promoters of both housekeeping and tissue-specific genes. Differential expression gene analysis revealed that BEAF32 knockout resulted in abnormal activation of non-ovarian tissue-specific genes in the ovaries, implying that BEAF32 regulates tissue-specific patterns of gene expression. Among upregulated genes there were not only BEAF32-associated genes suggesting direct and indirect mechanisms of BEAF32-mediated expression control. We discovered that BEAF32 occupied many ovary-specific gene promoters and acted as a positive regulator of the cell-cycle regulatory kinase Polo expression. To reveal the possible role of BEAF32 in the pathway mediated by Piwi-interacting RNAs (piRNAs) we performed an analysis of ovarian small RNAs in the BEAF32 null mutants and revealed a strong decrease in the production of piRNAs from the 3R subtelomeric region. Our data suggest that BEAF32-containing chromatin complex located upstream of the subtelomeric repeats preserves transcriptional and chromatin integrity of this domain in the germline. BEAF32 was also found upstream of flamenco, a largest piRNA source locus in the follicular cells, and is required for the cell-specific transcription of the flam locus. Conclusions: These findings suggest that BEAF32 represses the ectopic expression of developmental and tissue-specific genes in the ovaries. BEAF32 regulates polo kinase and other oogenesis-related genes. BEAF32 insulators have been revealed to play a specific ovarian role in the maintenance of piRNA-producing loci. Our results provide strong support for the importance of BEAF32 insulator protein in determining the proper landscape of tissue-specific gene expression and locus-specific function realization.

Project description:Insulators delimit independent transcriptional domains within genomes by constraining enhancer and silencer action. These transcriptional effects depend upon DNA recognition by insulator binding proteins that recruit partners that protect against inappropriate long range modulation of non-target promoters. Insulator binding proteins are broadly expressed during development, with largely constitutive binding to thousands of genomic sites. Yet, tissue-specific transcriptional changes result from the loss of individual insulator binding proteins. To understand the molecular basis for such effects, we are studying the classic Drosophila insulator protein Suppressor of Hairy-wing [Su(Hw)]. Genetic studies show that loss of this broadly expressed insulator protein prevents oocyte development. To determine the basis for the block in oogenesis, we coupled transcriptional analyses in su(Hw) mutant ovaries with genome-wide definition of Su(Hw) binding in this tissue. These studies identified 71 direct targets of Su(Hw) regulation, with nearly 70% of these genes showing increased RNA accumulation when Su(Hw) is lost. Surprisingly, derepressed Su(Hw) target genes correspond to genes normally highly expressed in neural tissues, suggesting that Su(Hw) has a critical role in silencing neural genes in the ovary. Support for this postulate was obtained by genetic studies. We found that oocyte production was restored in su(Hw) mutant females that carry a deletion of one allele of the elav family RNA binding protein 9 (Rbp9) gene. These su(Hw) null oocytes can be fertilized, with evidence that embryos lacking Su(Hw) show compromised development. Our studies extend the known transcriptional activities of Su(Hw), indicating that Su(Hw) can function as an insulator, activator and repressor, the latter function being essential for oogenesis. These findings highlight that insulator proteins are versatile transcriptional regulatory proteins, suggesting that tissue specific contributions to transcription result from direct regulation of individual genes. Ovaries for RNA isolation were dissected from 4-6 hour old virgin females of wild type, su(Hw)f/v (fertile), su(Hw)2/v (sterile) and su(Hw)Pb/2 (sterile) Drosophila melanogaster. At this stage of development, ovaries only contain egg chamber stages 1-8. Loss of Su(Hw) causes apoptosis at stage 9. Thus, the experimental design compares transcriptionl changes in the ovary prior to induction nof apoptosis in su(Hw) mutants.

Project description:Insulators delimit independent transcriptional domains within genomes by constraining enhancer and silencer action. These transcriptional effects depend upon DNA recognition by insulator binding proteins that recruit partners that protect against inappropriate long range modulation of non-target promoters. Insulator binding proteins are broadly expressed during development, with largely constitutive binding to thousands of genomic sites. Yet, tissue-specific transcriptional changes result from the loss of individual insulator binding proteins. To understand the molecular basis for such effects, we are studying the classic Drosophila insulator protein Suppressor of Hairy-wing [Su(Hw)]. Genetic studies show that loss of this broadly expressed insulator protein prevents oocyte development. To determine the basis for the block in oogenesis, we coupled transcriptional analyses in su(Hw) mutant ovaries with genome-wide definition of Su(Hw) binding in this tissue. These studies identified 71 direct targets of Su(Hw) regulation, with nearly 70% of these genes showing increased RNA accumulation when Su(Hw) is lost. Surprisingly, derepressed Su(Hw) target genes correspond to genes normally highly expressed in neural tissues, suggesting that Su(Hw) has a critical role in silencing neural genes in the ovary. Support for this postulate was obtained by genetic studies. We found that oocyte production was restored in su(Hw) mutant females that carry a deletion of one allele of the elav family RNA binding protein 9 (Rbp9) gene. These su(Hw) null oocytes can be fertilized, with evidence that embryos lacking Su(Hw) show compromised development. Our studies extend the known transcriptional activities of Su(Hw), indicating that Su(Hw) can function as an insulator, activator and repressor, the latter function being essential for oogenesis. These findings highlight that insulator proteins are versatile transcriptional regulatory proteins, suggesting that tissue specific contributions to transcription result from direct regulation of individual genes.

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Insulator BEAF32 regulates expression of tissue-specific genes and piRNA source loci in the Drosophila ovaries [ChIP-seq]

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