The tumor suppressor Brat controls neuronal lineages by inhibiting the transcription factors Deadpan and Zelda
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PROVIDER: PRJNA413144 | ENA |
REPOSITORIES: ENA
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Project description:The TRIM-NHL protein Brain tumor (Brat) acts as a tumor suppressor in the Drosophila brain, but how it suppresses tumor formation is not completely understood. Here, we combine temperature controlled brat RNAi with transcriptome analysis to identify the immediate brat targets in Drosophila neuroblasts. Besides the known target Deadpan (Dpn), our experiments identify the transcription factor Zelda (Zld) as a critical target of brat. Our data show that Zld is expressed in neuroblasts and required to allow re-expression of Dpn in transit amplifying intermediate neural progenitors. Upon neuroblast division, Brat is enriched in one daughter cell where its NHL domain directly binds to specific motifs in the 3’UTR of dpn and zld mRNA to mediate their degradation. In brat mutants, both Dpn and Zld continue to be expressed, but inhibition of either transcription factor prevents tumorigenesis. Our genetic and biochemical data indicate that Dpn inhibition requires higher Brat levels than Zld inhibition and suggest a model where stepwise post-transcriptional inhibition of distinct factors ensures sequential generation of fates in a stem cell lineage.
2017-11-28 | GSE104592 | GEO
Project description:During the first stages of development, the fertilized germ cells rapidly transition to totipotency. Maternally deposited mRNAs encode the proteins necessary for reprogramming the transcriptionally quiescent zygotic genome during this maternal-to-zygotic transition (MZT). The transcription factor Zelda is essential for this reprogramming in the Drosophila embryo. Zelda is necessary for transcriptional activation of the zygotic genome, and the absence of Zelda leads to embryonic lethality during the MZT. Excess Zelda activity is also lethal to the embryo, demonstrating that Zelda levels must be precisely controlled during early development. Because Zelda is encoded by a maternally deposited mRNA, Zelda levels in the embryo are controlled at the level of translation. To understand how levels of this essential reprogramming factor were regulated to allow for embryonic development and zygotic genome activation, we investigated the factors that regulated translation of zelda. Brain Tumor (BRAT) is a translational regulator that was previously shown to bind to zelda mRNA in the embryo. We showed that BRAT functions to repress zelda translation, as embryos deficient for maternal BRAT activity prematurely express Zelda. We further showed that in the larval brain, BRAT similarly regulates Zelda levels and identified specific BRAT-binding sites that mediate these effects. Thus, BRAT regulates Zelda in multiple tissues. Because both too little and too much Zelda are lethal to the embryo, we hypothesized that precocious expression of this transcriptional activator might be capable of driving precocious activation of the zygotic genome, leading to embryonic lethality. To test this hypothesis, we performed single embryo RNA-seq at distinct nuclear cycles throughout zygotic genome activation (NC10, NC12, NC13, and NC14) in control and brat-mutant embryos. Our results conclusively demonstrated that in embryos lacking functional BRAT, Zelda target genes were not prematurely activated. Rather, these genes were expressed normally, but become significantly upregulated at nuclear cycle 14, when the division cycle slows. Our data support a model in which zygotic genome activation requires precise coordination between expression of reprogramming factors, such as Zelda, and the slowing of the cell cycle.
2022-06-17 | GSE197582 | GEO
Project description: Not available
| S-EPMC5757284 | biostudies-literature
Project description:In nearly all metazoans, the earliest stages of development are controlled by maternally deposited mRNAs and proteins. The zygotic genome only becomes transcriptionally active hours later. Transcriptional activation is tightly coordinated with the degradation of maternally provided mRNAs during this maternal-to-zygotic transition (MZT). In Drosophila melanogaster, the transcription factor Zelda plays an essential role in widespread activation of the zygotic genome. While Zelda expression is required both maternally and zygotically, the mechanisms by which it functions both during and after the MZT remain unclear. Zelda is a large protein with six C2H2 zinc fingers, but no additional identified domains or predicted enzymatic activities. Using Cas9-mediated genome editing to generate targeted mutations in Zelda, we determined the functional relevance of protein domains conserved amongst Zelda orthologs. Generating these mutations in vivo revealed that neither a conserved N-terminal zinc finger nor an acidic patch were required for activity. Similarly, using a variety of Cas9-enabled approaches we showed that a previously identified splice isoform of zelda is dispensable for viability, and the predicted protein product is not expressed at detectable levels. By contrast, we identified a highly conserved zinc-finger domain that is essential for the maternal, but not zygotic functions of Zelda. A mutation in this zinc-finger domain does not interfere with the capacity of Zelda to activate transcription, but rather leads to a hyperactive form of the protein and enhanced Zelda-dependent gene expression. Embryos inheriting this allele from their mothers die late in embryogenesis. These data define a protein domain critical for controlling Zelda activity and, for the first time, identify a separation between the maternal and zygotic requirements for Zelda. This demonstrates that highly regulated levels of Zelda activity are essential for establishing the developmental program during the MZT and that failure to precisely execute this program leads to embryonic lethality.
2017-11-28 | GSE103914 | GEO
Project description:During early Drosophila embryogenesis, the essential pioneer factor Zelda defines hundreds of cis-regulatory regions and in doing so reprograms the zygotic transcriptome. While Zelda is essential later in development, it is unclear how the ability of Zelda to define cis-regulatory regions is shaped by cell-type specific chromatin architecture established during differentiation. Asymmetric division of neural stem cells (neuroblasts) in the fly brain provide an excellent paradigm for investigating the cell-type specific functions of this pioneer factor. Zelda is expressed in neuroblasts, and we show that Zelda synergistically functions with Notch to maintain neuroblasts in an undifferentiated state. Zelda misexpression can reprogram progenitor cells to neuroblasts, but this capacity is limited by transcriptional repressors critical for progenitor commitment. Zelda genomic occupancy in neuroblasts is reorganized as compared to the embryo, despite sharing many target genes in these two developmental stages. This reorganization is likely driven by differences in chromatin accessibility and cofactor availability. We propose that Zelda regulates essential transitions in the neuroblasts and embryo through a shared gene regulatory network by defining cell-type specific enhancers.
2021-11-05 | GSE150931 | GEO
Project description:A long-standing question in the field of embryogenesis is how the zygotic genome is precisely activated by maternal factors, allowing normal early embryonic development. We have previously shown that N6-methyladenine (6mA) DNA modification is highly dynamic in early Drosophila embryos and forms an epigenetic mark. However, little is known about how 6mA-formed epigenetic information is decoded. Here we report that the Fox-family protein Jumu binds 6mA-marked DNA and acts as a maternal factor to regulate the maternal-to-zygotic transition. We find that zelda encoding the pioneer factor Zelda is marked by 6mA. Our genetic assays suggest that Jumu controls the proper zygotic genome activation (ZGA) in early embryos, at least in part, by regulating zelda expression. Thus, our findings not only support that the 6mA-formed epigenetic can be read by specific transcription factors, but also uncover a mechanism by which the Jumu regulates ZGA partially through Zelda in early embryos.
2019-04-18 | GSE86795 | GEO
Project description:Reprogramming cell fate during the first stages of embryogenesis requires that transcriptional activators gain access to the genome and remodel the zygotic transcriptome. Nonetheless, it is not clear if the continued activity of these pioneering factors is required throughout zygotic genome activation or if they are only required early to establish cis-regulatory regions. To address this question, we developed an optogenetic strategy to rapidly and reversibly inactivate the master regulator of genome activation in Drosophila, Zelda. Using this strategy, we demonstrated that continued Zelda activity is required throughout genome activation. We showed that Zelda binds DNA in the context of nucleosomes and suggest that this allows Zelda to occupy the genome despite the rapid division cycles in the early embryo. These data identify a powerful strategy to inactivate transcription factor function during development and suggest that reprogramming in the embryo may require specific, continuous pioneering functions to activate the genome.
2019-02-06 | GSE121157 | GEO
Project description:ETS1 acts as a tumor suppressor in breast cancer by inhibiting growth-related factors
| PRJNA417488 | ENA
Project description:Long non-coding RNAs have been implicated in many of the hallmarks of cancer. We previously annotated lncRNA152 (lnc152; a.k.a. DRAIC) and demonstrated its roles in proliferation, cell cycle progression, and regulation of the estrogen signaling pathway in breast cancer cells. Herein, we found that lnc152 is highly upregulated in luminal breast cancers, but is downregulated in triple-negative breast cancers (TNBC). Using a set of complementary experimental approaches, we found that knockdown of lnc152 promotes cell migration and invasion in luminal breast cancer cell lines. In contrast, ectopic expression of lnc152 inhibits growth, migration, invasion, and angiogenesis in TNBC cell lines. In xenograft studies in mice, lnc152 inhibited the growth and metastasis of TNBC cells. Transcriptome analysis of the xenografts indicated that lnc152 downregulates genes regulating cancer-related phenotypes, including angiogenesis. Using RNA-pull down assays coupled with LC-MS/MS analysis, we identified RBM47, a known tumor suppressor protein in breast cancer, as a lnc152-interacting protein. We found that lnc152 suppresses the aggressive phenotypes of TNBC cells by regulating the expression of RBM47. Collectively, our results demonstrate that lnc152 is an angiogenesis-inhibiting tumor suppressor that attenuates the aggressive cancer-related phenotypes found in TNBC.
2022-11-09 | GSE193634 | GEO
Project description:Pioneer factors such as Zelda initiate zygotic transcription within Drosophila early embryos, but whether other factors also support this dynamic patterning process is unclear. Odd-paired (Opa) is a zinc-finger transcription factor expressed during cellularization, shown to act as timing factor to control pair-rule to segmental patterning transition along the anterior-posterior (AP) axis. We found Opa regulates expression through an enhancer active along the dorso-ventral axis (sog_Distal), specifically, to support its late embryonic expression. Opa chromatin immunoprecipitation identified occupancy at this enhancer sequence as well widespread binding throughout the genome, comparable to Zelda. Furthermore, chromatin assays (ATAC-seq) demonstrate that Opa, like Zelda, influences accessibility and has both common as well as distinct target sequences. opa mutants also exhibit DV and AP patterning changes suggesting Opa acts broadly. This study suggests Opa is a late-acting, pioneer factor whose action follows Zelda to herald in a second wave of zygotic gene expression. NIH Grants R35GM118146 and R03HD097535 to A.S.
2020-08-02 | GSE140722 | GEO