Post-transkriptionale Regulation von egl-1 BH3-only
Zusammenfassung der Projektergebnisse
The C. elegans cell death fate is highly suitable for the dissection of mechanisms involved in the control of gene expression during animal development. Based on our preliminary findings and published work, we had proposed the following working model for gene expression control of the cell death fate determinant egl-1 BH3-only: In cell death lineages, the egl-1 locus becomes primed for transcriptional activation at least one cellular generation prior to apoptosis, and that this results in significant transcript accumulation within mothers of cells that are programmed to die. Most of these transcripts are targeted for degradation and/or translational repression by miRNAs and/or RBPs. The level of egl-1 transcription varies between different lineages since different sets of transcription factors are responsible. We had also proposed that repression via miRNAs is necessary to keep synthesis of EGL-1 protein ‘in check’, thus providing a key buffer for differences in transcription in different lineages. Furthermore, we had proposed that through this mechanism, a similar, low level of EGL-1 protein required for cellular polarization is synthesized in mothers of cells programmed to die. After mother cell division, EGL-1 protein synthesis increases in the daughter programmed to die due to what we had proposed to be a combination of increased transcription, increased mRNA stabilization and increased translational efficiency that is dependent on compartmentalization of egl-1 mRNA into perinuclear ‘translation factories’. Conversely, in the sibling programmed to survive, an increase in EGL-1 protein synthesis is prevented due to decreased mRNA stabilization. Of note, once a mother cell has divided, the smaller daughter undergoes apoptosis in an EGL-1-dependent manner within 20-30 min. Therefore, these events must occur within a very short timeframe. Important issues that remained to be resolved included the following: a) Which factors other than miRNAs are required to maintain post-transcriptional repression of egl-1 in mothers of cells programmed to die? b) How is post-transcriptional regulation of egl-1 in mothers modulated to permit a level of expression that is sufficient to regulate cell polarity, but not so high as to trigger cell death? c) How is post-transcriptional regulation of egl-1 controlled to permit high level expression specifically within cells programmed to die? d) How is perinuclear localization of egl-1 transcript achieved in cells programmed to die? e) Is perinuclear localization necessary for efficient expression of egl-1? f) How is post-transcriptional regulation of egl-1 controlled to prevent expression in siblings programmed to survive? g) How do different lineages cope with different levels of egl-1 mRNA? In order to address these questions, we proposed to systematically identify regulatory factors (i.e. cisacting elements within the egl-1 transcript and the trans-acting factors that associate with them) that affect egl-1 expression (Aim 1). Furthermore, we proposed to investigate the mechanisms whereby these interactions affect egl-1 expression. To that end, we proposed to develop genetic tools that enable us to image egl-1 mRNA and nascent protein translation in real time in live embryos (Aim 2).
Projektbezogene Publikationen (Auswahl)
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PUF-8, a C. elegans ortholog of the RNA-binding proteins PUM1 and PUM2, is required for robustness of the cell death fate. Development, 150(19).
Xu, Jimei; Jiang, Yanwen; Sherrard, Ryan; Ikegami, Kyoko & Conradt, Barbara
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A genetic screen identifies C. elegans eif-3.H and hrpr-1 as pro-apoptotic genes and potential activators of egl-1 expression. microPublication Biology.
Jiang, Y. & Conradt, B.
