The TNFR Wengen regulates the FGF pathway by an unconventional mechanism

Unveiling the molecular mechanisms of receptor activation has led to much understanding of development as well as the identification of important drug targets. We use the Drosophila tracheal system to study the activity of two families of widely used and conserved receptors, the TNFRs and the RTK-FGFRs. Breathless, an FGFR, controls the program of differentiation of the tracheal terminal cells in response to ligand activation. Here we identify a role for Wengen, a TNFR, in repressing the terminal cell program by regulating the MAPK pathway downstream of Breathless. We find that Wengen acts independently of both its canonical ligand and downstream pathway genes. Wengen does not stably localise at the membrane and is instead internalised-a trafficking that seems essential for activity. We show that Breathless and Wengen colocalise in intracellular vesicles and form a complex. Furthermore, Wengen regulates Breathless accumulation, possibly regulating Breathless trafficking and degradation. We propose that, in the tracheal context, Wengen interacts with Breathless to regulate its activity, and suggest that such unconventional mechanism, involving binding by TNFRs to unrelated proteins, may be a general strategy of TNFRs.© 2023. Springer Nature Limited

Moving towards an organized cervical cancer screening: costs and impact

Background: HPV screening has been shown to be more cost-effective than cytology screening under most scenarios. Furthermore, it should be offered only in organized programmes with good quality assurance mechanisms. This study analyses the comparative cost of the current policy of opportunistic cytology screening vs. a hypothetical organized programme based on primary HPV screening. Methods: Total cervical cancer expenditure was defined as the sum of three cost elements: (i) direct (medical and non-medical) costs, obtained from a calibrated Markov model of the natural history of HPV and cervical cancer; (ii) programmatic costs, estimated based on other organized screening programmes; and (iii) indirect costs, extrapolated from previously published data. Results: Organized HPV screening at 5-year intervals costs consistently less across all coverage levels than opportunistic cytology screening at 3-year intervals. The current annual direct medical cost to the public health system of the opportunistic cytology at 40% coverage is estimated at (sic)33.2 per woman screened aged 25-64. Under an organized programme of primary HPV screening at 70% coverage, the cost is estimated to be (sic)18.4 per woman screened aged 25-64. Conclusion: Our study concludes that the economic resources currently devoted to providing opportunistic cytology screening to 40% of the target population at 3-year intervals could be more effectively used to screen 70% of the target population at 5-year intervals by switching to an organized programme based on primary HPV screening. This finding is of relevance to other European countries or regions with similar screening policies and health infrastructures

Structural basis of high-order oligomerization of the cullin-3 adaptor SPOP.

Protein ubiquitination in eukaryotic cells is mediated by diverse E3 ligase enzymes that each target specific substrates. The cullin E3 ligase complexes are the most abundant class of E3 ligases; they contain various cullin components that serve as scaffolds for interaction with substrate-recruiting adaptor proteins. SPOP is a BTB-domain adaptor of the cullin-3 E3 ligase complexes; it selectively recruits substrates via its N-terminal MATH domain, whereas its BTB domain mediates dimerization and interactions with cullin-3. It has recently been recognized that the high-order oligomerization of SPOP enhances the ubiquitination of substrates. Here, a dimerization interface in the SPOP C-terminus is identified and it is shown that the dimerization interfaces of the BTB domain and of the C-terminus act independently and in tandem to generate high-order SPOP oligomers. The crystal structure of the dimeric SPOP C-terminal domain is reported at 1.5 Å resolution and it is shown that Tyr353 plays a critical role in high-order oligomerization. A model of the high-order SPOP oligomer is presented that depicts a helical organization that could enhance the efficiency of substrate ubiquitination

The Tnt1 Retrotransposon Escapes Silencing in Tobacco, Its Natural Host

Retrotransposons' high capacity for mutagenesis is a threat that genomes need to control tightly. Transcriptional gene silencing is a general and highly effective control of retrotransposon expression. Yet, some retrotransposons manage to transpose and proliferate in plant genomes, suggesting that, as shown for plant viruses, retrotransposons can escape silencing. However no evidence of retrotransposon silencing escape has been reported. Here we analyze the silencing control of the tobacco Tnt1 retrotransposon and report that even though constructs driven by the Tnt1 promoter become silenced when stably integrated in tobacco, the endogenous Tnt1 elements remain active. Silencing of Tnt1-containing transgenes correlates with high DNA methylation and the inability to incorporate H2A.Z into their promoters, whereas the endogenous Tnt1 elements remain partially methylated at asymmetrical positions and incorporate H2A.Z upon induction. Our results show that the promoter of Tnt1 is a target of silencing in tobacco, but also that endogenous Tnt1 elements can escape this control and be expressed in their natural host

Dos poetas frente a la muerte

Publicat a Destino.Parla dels llibres: 'La muerte o la vida' de Manuel Pinillos i 'El retorno' de J. A. Goytisolo

Glucocorticoid-induced DNA demethylation and gene memory during development

Glucocorticoid hormones were found to regulate DNA demethylation within a key enhancer of the rat liver-specific tyrosine aminotransferase (Tat) gene. Genomic footprinting analysis shows that the glucocorticoid receptor uses local DNA demethylation as one of several steps to recruit transcription factors in hepatoma cells. Demethylation occurs within 2–3 days following rapid (<1 h) chromatin remodeling and recruitment of a first transcription factor, HNF-3. Upon demethylation, two additional transcription factors are recruited when chromatin is remodeled. In contrast to chromatin remodeling, the demethylation is stable following hormone withdrawal. As a stronger subsequent glucocorticoid response is observed, demethylation appears to provide memory of the first stimulation. During development, this demethylation occurs before birth, at a stage where the Tat gene is not yet inducible, and it could thus prepare the enhancer for subsequent stimulation by hypoglycemia at birth. In vitro cultures of fetal hepatocytes recapitulate the regulation analyzed in hepatoma cells. There fore, demethylation appears to contribute to the fine-tuning of the enhancer and to the memorization of a regulatory event during development

The Drosophila transcription factor tramtrack (TTK) interacts with Trithorax-like (GAGA) and represses GAGA-mediated activation

In this study, we report the interaction of the Drosophila transcription factors Trithorax-like (GAGA) and tramtrack (TTK). This interaction is documented both in vitro, through GST pull-down assays, as well as in vivo, in yeast and Schneider S2 cells. GAGA and TTK share in common the presence of an N-terminal POZ/BTB domain that was found to be necessary and sufficient for GAGA–TTK interaction. Structural models that could account for this interaction are discussed. GAGA is known to activate the expression of many genes in Drosophila. On the other hand, TTK was proposed to act as a maternally provided repressor of several pair-rule genes, such as even-skipped (eve). As with many Drosophila genes, eve contains at its promoter region binding sites for GAGA and TTK. Here, in transient expression experiments, we showed that GAGA activates transcription from the eve stripe 2 promoter element and that TTK inhibits this GAGA-dependent activation. Repression by TTK of the eve promoter requires its activation by GAGA and depends on the presence of the POZ/BTB domains of TTK and GAGA. These results indicate that GAGA–TTK interaction contributes to the regulation of gene expression in Drosophila

The GAGA factor of Drosophila interacts with SAP18, a Sin3-associated polypeptide

SAP18, a polypeptide associated with the Sin3–HDAC co-repressor complex, was identified in a yeast two-hybrid screen as capable of interacting with the Drosophila GAGA factor. The interaction was confirmed in vitro by glutathione S-transferase pull-down assays using recombinant proteins and crude SL2 nuclear extracts. The first 245 residues of GAGA, including the POZ domain, are necessary and sufficient to bind dSAP18. In polytene chromosomes, dSAP18 and GAGA co-localize at a few discrete sites and, in particular, at the bithorax complex where GAGA binds some silenced polycomb response elements. When the dSAP18 dose is reduced, flies heterozygous for the GAGA mutation Trl(67) show the homeotic transformation of segment A6 into A5, indicating that GAGA–dSAP18 interaction contributes to the functional regulation of the iab-6 element of the bithorax complex. These results suggest that, through recruitment of the Sin3–HDAC complex, GAGA might contribute to the regulation of homeotic gene expression