Project description:Variability in lifespan among individuals of the same species is a poorly understood phenomenon. Even among isogenic C. elegans reared in identical environments, we observe considerable variance in lifepsan. To better understand the differences in gene expression that underly this variability, we characterized the transcriptomes associated with long vs. short lifespan. We isolated the longest- and shortest-lived members from their respective populations using biomarkers of aging--predictive markers whose expression levels correlate with an individual's future lifespan. Specifically, we sorted animals by the expression of lin-4p::GFP, mir-243p::GFP, mir-240/786p::GFP, and autofluorescence. All populations were chronologically five days old at time of sorting. We subsequently compared the transcriptomes of future lifespan within and between different biomarkers to identify a gene expression signature of future lifespan.
Project description:CD8 effector T cells with a CD127hi KLRG1- phenotype are considered precursors to the long-lived memory pool, while KLRG1+ CD127low cells are viewed as short-lived effectors. Nevertheless, we and others have shown that a KLRG1+ CD127low population persists into the memory phase and that these T cells (termed long-lived effector cells or LLEC) display robust protective function during acute re-challenge with bacteria or viruses. Whether these T cells represent a true memory population or are instead a remnant effector cell population that failed to undergo initial contraction has remained unclear. Here, we show that LLEC from mice express a distinct phenotypic and transcriptional signature that shares characteristics of both early effectors and long-lived memory cells. Furthermore, we find that LLEC are exclusively derived from day 12 KLRG1+ effector cells. Our work challenges the concept that the KLRG1+ CD127low population is dominated by short-lived cells and shows that KLRG1 downregulation is not a prerequisite to become a long-lived protective memory T cell.
Project description:Rapid protein degradation enables cells to quickly modulate protein abundance in response to stimuli. Previous studies have generally sought to delineate basic features of proteome turnover. A focused map of short-lived proteins, however, remains a missing piece of the human proteome. To begin to address this, we combined cycloheximide chase assays with advanced high-throughput quantitative proteomics to map short-lived proteins in four genetically distinct human cell lines. Apparent half-lives of ≤ 8 hr were measured for 1,017 proteins. Systematic analyses revealed general properties of short-lived proteins (e.g., enriched in substrate recognition subunits of E3 ubiquitin ligase complexes, thermally instable, evolutionarily younger). We further quantified 103 proteins with widely different stabilities among cell lines. Of these, we show that truncated forms of ATRX and GMDS were expressed in U2OS and HCT116 cells, respectively, which had shorter half-lives than their full-length counterparts. This study provides a large-scale resource of human short-lived proteins in cultured cells, leading to untapped avenues of protein regulation for therapeutic intervention.
Project description:The aim of this stuy was to investigate the effect of H3.3 deficiency on gene transcription in both a wild-type and a long-lived mutant context in C. elegans.
Project description:Targeted proTargeted protein degradation has recently emerged as a novel option in drug discovery. Natural protein half-life is expected to affect the efficacy of degrading agents, but it has not been systematically explored to what extent it influences target protein degradation. Using mathematical modelling of protein degradation, we demonstrate that the natural half-life of a target protein has a dramatic effect on the level of protein degradation induced by a PROTAC which can pose significant hurdles to screening efforts. Moreover, we show that upon screening for degraders of short-lived proteins, agents that stall protein synthesis, such as GSPT1 degraders and generally cytotoxic compounds, deceptively appear as protein degrading agents. This is exemplified by the disappearance of short-lived proteins such as MCL1 and MDM2 upon GSPT1 degradation and upon treatment with cytotoxic agents such as doxorubicin. These findings have implications for target selection as well as for the type of control experiments required before concluding that a novel agent works as a bone-fide targeted protein degrader. tein degradation has recently emerged as a novel option in drug discovery. Natural protein half-life is expected to affect the efficacy of degrading agents, but it has not been systematically explored to what extent it influences target protein degradation. Using mathematical modelling of protein degradation, we demonstrate that the natural half-life of a target protein has a dramatic effect on the level of protein degradation induced by a PROTAC which can pose significant hurdles to screening efforts. Moreover, we show that upon screening for degraders of short-lived proteins, agents that stall protein synthesis, such as GSPT1 degraders and generally cytotoxic compounds, deceptively appear as protein degrading agents. This is exemplified by the disappearance of short-lived proteins such as MCL1 and MDM2 upon GSPT1 degradation and upon treatment with cytotoxic agents such as doxorubicin. These findings have implications for target selection as well as for the type of control experiments required before concluding that a novel agent works as a bone-fide targeted protein degrader.
Project description:Purpose: We used RNA-Seq to compare the gene expression profiles in two long-lived C. elegans strains: (1) animals with a loss-of-function mutation in the hsb-1 gene, and (2) animals overexpressing hsf-1 under its endogenous promoter. Previous studies indicated that life span extension in both these strains is hsf-1-dependent. Methods: mRNA-Seq profiles for three biological replicates each of day 1 adult wild-type (N2 strain), hsb-1 mutant and hsf-1 overexpression strains were generated using 50 bp single-end sequencing on an Illumina HiSeq 2500 platform. The sequencing reads that passed quality control were aligned to the C. elegans reference transcriptome (WS220 release) using Bowtie 2 and splicing junctions were mapped using TopHat. Cufflinks was used to calculate FPKM values and CuffDiff 2 was used to identify differentially expressed genes based on the following two criteria: false discovery rate (FDR)-adjusted p value < 0.05 and fold-change ≥ 1.5. Results: Using our mRNA-Seq workflow, we mapped at least 14 million reads per sample to the C. elegans transcriptome at greater than 96 percent alignment rate for the raw reads. Expression of 7,478 genes was found to be significantly altered in the hsf-1 overexpression strain relative to wild-type worms, while only 1,855 genes had singnificantly different expression in the hsb-1 mutant strain relative to wild-type. Using our criterion of ≥ 1.5-fold change in gene expression, we found 1,820 and 662 genes to be differentially expressed relative to wild-type in hsf-1 overexpression and hsb-1 mutant strains, respectively. The 247 genes that were differentially expressed in both hsf-1 overexpression and hsb-1 mutant strains showed a strongly correlated expression pattern in the two strains. Conclusions: hsf-1 overexpression induces global transcriptional suppression in C. elegans. Genetic ablation of hsb-1 produces similar life span extension in worms as hsf-1 overexpression, but alters expression of a much smaller subset of the C. elegans transcriptome. Hence, HSB-1 is a specific regulator of the transactivation potential of HSF-1 that selectively modulates gene expression relevant to longevity determination in worms.