Conservation and divergence of the p53 gene regulatory network between mice and humans.
Ontology highlight
ABSTRACT: Understanding the p53 tumor suppressor pathway remains crucial for the design of anticancer strategies. Studies in human tumors and mouse models help to unravel the molecular mechanisms that underlie the p53 signaling pathway. Yet, the p53 gene regulatory network (GRN) is not the same in mice and humans. The comparison of the regulatory networks of p53 in mice and humans reveals that gene up- and down-regulation by p53 are distinctly affected during evolution. Importantly, gene up-regulation by p53 underwent more rapid evolution and gene down-regulation has been evolutionarily constrained. This difference stems from the two major mechanisms employed by p53 to regulate gene expression: up-regulation through direct p53 target gene binding and indirect down-regulation through the p53-p21-DREAM pathway. More than 1000 genes have been identified to differ in their p53-dependent expression between mice and humans. Analysis of p53 gene expression profiles and p53 binding data reveal that turnover of p53 binding sites is the major mechanism underlying extensive variation in p53-dependent gene up-regulation. Only a core set of high-confidence genes appears to be directly regulated by p53 in both species. In contrast to up-regulation, p53-induced down-regulation is well conserved between mice and humans and controls cell cycle genes. Here a curated data set is provided that extends the previously established web-atlas at www.targetgenereg.org to assess the p53 response of any human gene of interest and its mouse ortholog. Taken together, the analysis reveals a limited translation potential from mouse models to humans for the p53 GRN.
Project description:While myelin is commonly assessed in mice as a model for humans, it remained unclear to which extent their myelin protein composition is similar. We analyzed the proteome of myelin biochemically purified from human white matter by two steps of discontinuous sucrose density gradient centrifugation intermitted by osmotic shocks. We utilized a data-independent acquisition (DIA) workflow with alternating low and elevated energy (MSE) and an ion mobility-enhanced version thereof (referred to as UDMSE) to achieve both, a correct quantification of exceptionally abundant myelin proteins and a comprehensive coverage of the myelin proteome. Label-free protein quantification revealed that the relative abundance of the structural myelin proteins PLP, MBP, CNP and SEPTIN8 correlates well with that in c57Bl/6N-mice. Conversely, multiple other proteins were identified exclusively or predominantly in human or mouse myelin. Species-dependent diversity of myelin protein composition can be instructive when translating from mouse models to humans.
Project description:PIERCE1, p53 induced expression 1 in Rb null cells, is a novel p53 target involved in the DNA damage response and cell cycle in mice. These facts prompted us to study the function of PIERCE1 with respect to p53-associated pathophysiology of cancer in humans. Unexpectedly, PIERCE1 did not respond to overexpression and activation of p53 in humans. In this study, we swapped p53 protein expression in human and mouse cells to find the clue of this difference between species. Human p53 expression in mouse cells upregulated PIERCE1 expression, suggesting that p53-responsive elements on the PIERCE1 promoter are crucial, but not the p53 protein itself. Indeed, in silico analyses of PIERCE1 promoters revealed that p53-responsive elements identified in mice are not conserved in humans. Consistently, chromatin immunoprecipitation-sequencing (ChIP-seq) analyses confirmed p53 enrichment against the PIERCE1 promoter region in mice, not in human cells. To complement the p53 study in mice, further promoter analyses suggested that the human PIERCE1 promoter is more similar to guinea pigs, lemurs, and dogs than to rodents. Taken together, our results confirm the differential responsiveness of PIERCE1 expression to p53 due to species differences in PIERCE1 promoters. The results also show partial dissimilarity after p53 induction between mice and humans.
Project description:Human myelin disorders are commonly studied in mouse models. Since both clades evolutionarily diverged approximately 85 million years ago, it is critical to know to what extent the myelin protein composition has remained similar. Here, we use quantitative proteomics to analyze myelin purified from human white matter and find that the relative abundance of the structural myelin proteins PLP, MBP, CNP, and SEPTIN8 correlates well with that in C57Bl/6N mice. Conversely, multiple other proteins were identified exclusively or predominantly in human or mouse myelin. This is exemplified by peripheral myelin protein 2 (PMP2), which was specific to human central nervous system myelin, while tetraspanin-2 (TSPAN2) and connexin-29 (CX29/GJC3) were confined to mouse myelin. Assessing published scRNA-seq-datasets, human and mouse oligodendrocytes display well-correlating transcriptome profiles but divergent expression of distinct genes, including Pmp2, Tspan2, and Gjc3. A searchable web interface is accessible via www.mpinat.mpg.de/myelin. Species-dependent diversity of oligodendroglial mRNA expression and myelin protein composition can be informative when translating from mouse models to humans.
Project description:While comparative functional genomic studies have shown that inter-species differences in gene expression can be explained by corresponding inter-species differences in genetic and epigenetic regulatory mechanisms, co-transcriptional mechanisms, such as alternative polyadenylation (APA), have received little attention. We characterized APA in lymphoblastoid cell lines from six humans and six chimpanzees by identifying and estimating the usage for 44,432 polyadenylation sites (PAS) in 9518 genes. Although APA is largely conserved, 1705 genes showed significantly different PAS usage (FDR 0.05) between species. Genes with divergent APA also tend to be differentially expressed, are enriched among genes showing differences in protein translation, and can explain a subset of observed inter-species protein expression differences that do not differ at the transcript level. Finally, we found that genes with a dominant PAS, which is used more often than other PAS, are particularly enriched for differentially expressed genes.
Project description:Differences in gene regulation contribute to phenotypic differences between humans and other primates. While co-transcriptional gene regulatory mechanisms such as alternative polyadenylation (APA) can help explain how variation in gene regulation manifests, such mechanisms remain understudied. We measured polyadenylation site (PAS) usage in a panel of 6 human and 6 chimpanzee lymphoblastoid cell lines (LCLs). While APA is largely conserved between humans and chimpanzees, genes with divergent APA patterns are enriched among differentially expressed and differentially translated genes. Differential usage of 3’ UTR and intronic PAS are both significantly correlated with differential mRNA expression effect sizes but in opposite directions. For many genes, there is one PAS dominant, meaning it is used much more often than others. The dominant PAS for these gene is overwhelmingly shared between species, however, differences in dominant PAS are enriched for genes with expression differences. Finally, through post-translational mechanisms, we believe APA contributes to genes differentially expressed at the protein level but not in mRNA. As this is the first primate comparative study of APA, our study establishes APA as a key mechanism underlying the genetic regulation of gene and protein expression levels in primates.
Project description:The tumor-suppressing transcription factor p53 is highly conserved at the protein level and plays a key role in the DNA damage response. One important aspect of p53 regulation is its dynamics in response to DNA damage, which include oscillations. Here, we observe that, while the qualitative oscillatory nature of p53 dynamics is conserved across cell lines derived from human, monkey, dog, mouse, and rat, the oscillation period is variable. Specifically, rodent cells exhibit rapid p53 oscillations, whereas dog, monkey, and human cells show slower oscillations. Computational modeling and experiments identify stronger negative feedback between p53 and MDM2 as the driver of faster oscillations in rodents, suggesting that the period of oscillation is a network-level property. In total, our study shows that despite highly conserved signaling, the quantitative features of p53 oscillations can diverge across evolution. We caution that strong amino acid conservation of proteins and transcriptional network similarity do not necessarily imply conservation of time dynamics.
Project description:The transition from vegetative growth to reproductive development is a complex process that requires an integrated response to multiple environmental cues and endogenous signals. In Arabidopsis thaliana, which has a facultative requirement for vernalization and long days, the genes of the autonomous pathway function as floral promoters by repressing the central repressor and vernalization-regulatory gene FLC. Environmental regulation by seasonal changes in daylength is under control of the photoperiod pathway and its key gene CO. The root and leaf crop species Beta vulgaris in the caryophyllid clade of core eudicots, which is only very distantly related to Arabidopsis, is an obligate long-day plant and includes forms with or without vernalization requirement. FLC and CO homologues with related functions in beet have been identified, but the presence of autonomous pathway genes which function in parallel to the vernalization and photoperiod pathways has not yet been reported. Here, this begins to be addressed by the identification and genetic mapping of full-length homologues of the RNA-regulatory gene FLK and the chromatin-regulatory genes FVE, LD, and LDL1. When overexpressed in A. thaliana, BvFLK accelerates bolting in the Col-0 background and fully complements the late-bolting phenotype of an flk mutant through repression of FLC. In contrast, complementation analysis of BvFVE1 and the presence of a putative paralogue in beet suggest evolutionary divergence of FVE homologues. It is further shown that BvFVE1, unlike FVE in Arabidopsis, is under circadian clock control. Together, the data provide first evidence for evolutionary conservation of components of the autonomous pathway in B. vulgaris, while also suggesting divergence or subfunctionalization of one gene. The results are likely to be of broader relevance because B. vulgaris expands the spectrum of evolutionarily diverse species which are subject to differential developmental and/or environmental regulation of floral transition.
Project description:We exploited traceable gene tagging in primary human T cells to establish the composition and dynamics of seven canonical TCR-induced protein signaling complexes (signalosomes) using affinity purification coupled with mass spectrometry (AP-MS). It unveiled how the LAT adaptor assembles higher-order molecular condensates and revealed that the proximal TCR-signaling network has a high degree of qualitative and quantitative conservation between human CD4+ and CD8+ T cells. Such systems-level conservation also extended across human and mouse T cells and unexpectedly encompassed protein-protein interaction stoichiometry. Independently of evolutionary considerations, our study suggests that a drug targeting the proximal TCR signaling network should behave similarly when applied to human and mouse T cells. However, considering that signaling differences likely exist between the distal TCR-signaling pathway of human and mouse, our fast-track AP-MS approach should be favored to determine the mechanism of action of drugs targeting human T cell activation. An opportunity is illustrated here using an inhibitor of the LCK protein tyrosine kinase as a proof-of-concept.
Project description:Asexual development is fundamental to the ecology and lifestyle of filamentous fungi and can facilitate both plant and human infection. In the filamentous fungal genus Aspergillus, the production of asexual spores is primarily governed by the BrlA-AbaA-WetA central regulatory cascade. The final step in this cascade, which is controlled by the WetA protein, not only governs cellular development (i.e., the morphological differentiation of spores) but also ensures its coupling with chemical development (i.e., the coordinated production and deposition of diverse secondary metabolites, such as aflatoxins, into spores). While the wetA gene is conserved across the genus Aspergillus, the structure and degree of conservation of the BrlA-AbaA-WetA regulatory cascade and the broader wetA gene regulatory network (GRN) remain largely unknown. We carried out comparative transcriptome analyses between wetA null mutant and wild type (WT) asexual spores in three representative species spanning the diversity of the genus Aspergillus: the genetic model A. nidulans, the agricultural pest A. flavus, and the human pathogen A. fumigatus. We discovered that WetA regulates asexual sporulation in all three species via a negative feedback loop that represses BrlA, the cascade’s first step. Furthermore, ChIP-seq experiments in A. nidulans asexual spores suggest that WetA is a DNA-binding protein that interacts with a novel regulatory element, which we term the WetA Response Element (WRE). Interestingly, the WRE is found completely conserved in the non-coding region upstream of the wetA translation start site of many diverse Aspergillus genomes. In contrast, several global transcriptional regulators, most notably those in the velvet complex (veA, velB, and laeA) known to regulate the coupling between asexual development and production of secondary metabolites, show species-specific regulatory patterns. These results suggest that the BrlA-AbaA-WetA cascade’s regulatory role in cellular and chemical development of asexual spores is functionally conserved, but that the WetA-associated GRN has diverged during Aspergillus evolution. This entry is for the RNA-seq data.