Caenorhabditis Elegans Host Cell Factor 1 Modulates Organismal Longevity And Stress Responses Via Coordinated Interactions With Multiple Nuclear Transcription Factors And Regulators

Aging is a complex process influenced by the environment and genotype. Numerous conserved genetic pathways and factors have been identified as key mediators of lifespan and stress responses in the nematode C. elegans. Host cell factor-1 (HCF-1) is a longevity and stress response modulator in worms. Mammalian HCF-1 is a vital transcriptional regulator which scaffolds diverse transcriptional regulatory complexes and controls gene expression. In C. elegans, HCF-1 is a repressor of the critical longevity determinant DAF-16, the homolog of mammalian FOXO transcription factors. The molecular partners of HCF-1 and the mechanisms whereby it modulates lifespan and stress responses have not been fully elucidated. My work implicated HCF-1 as a critical player in the regulatory mechanism linking DAF-16 and its coactivator SIR-2.1 in worms. Genetic analyses revealed that hcf-1 acts downstream of sir-2.1 to influence lifespan and oxidative stress response. Gene expression profiling uncovered a striking 80% overlap between the HCF-1- and SIR-2.1-regulated DAF16 target genes. Subsequent GO-term analyses of HCF-1 and SIR-2.1-coregulated DAF-16 targets suggested that HCF-1 and SIR-2.1 together regulate specific aspects of DAF-16mediated transcription important for aging and stress responses. My findings uncover a novel interaction between the key longevity determinants SIR-2.1 and HCF-1, and provide new insights into the complex regulation of DAF-16. SKN-1 transcription factor is an evolutionarily conserved protector against oxidative and xenobiotic stress and is a well-established pro-longevity factor. I demonstrated that SKN1 contributes to the enhanced oxidative stress resistance incurred by hcf-1 inactivation in a manner parallel to DAF-16. This functional interaction between HCF-1 and SKN-1 specifically occurs under excessive oxidant stress as SKN-1 is dispensable for the thermotolerance and long lifespan of hcf-1 mutants. HCF-1 represses the activation of SKN-1 to inhibit SKN-1 target genes involved in cellular detoxification pathways. To control SKN-1 activity, HCF-1 prevents nuclear accumulation of SKN-1 in response to oxidative stress. My findings reveal a new, context-specific regulatory relationship between the stress-response factors HCF-1 and SKN-1. Given that HCF-1, DAF-16, SIR-2.1, and SKN-1 are functionally conserved between C. elegans and mammals, my findings have important implications for the regulation of mammalian counterparts of these factors by HCF proteins

Direct conversion of mouse embryonic fibroblasts into functional keratinocytes through transient expression of pluripotency-related genes

The insufficient ability of specialized cells such as neurons, cardiac myocytes, and epidermal cells to regenerate after tissue damage poses a great challenge to treat devastating injuries and ailments. Recent studies demonstrated that a diverse array of cell types can be directly derived from embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), or somatic cells by combinations of specific factors. The use of iPSCs and direct somatic cell fate conversion, or transdifferentiation, holds great promise for regenerative medicine as these techniques may circumvent obstacles related to immunological rejection and ethical considerations. However, producing iPSC-derived keratinocytes requires a lengthy two-step process of initially generating iPSCs and subsequently differentiating into skin cells, thereby elevating the risk of cellular damage accumulation and tumor formation. In this study, we describe the reprogramming of mouse embryonic fibroblasts into functional keratinocytes via the transient expression of pluripotency factors coupled with directed differentiation. The isolation of an iPSC intermediate is dispensable when using this method. Cells derived with this approach, termed induced keratinocytes (iKCs), morphologically resemble primary keratinocytes. Furthermore they express keratinocyte-specific markers, downregulate mesenchymal markers as well as the pluripotency factors Oct4, Sox2, and Klf4, and they show important functional characteristics of primary keratinocytes. iKCs can be further differentiated by high calcium administration in vitro and are capable of regenerating a fully stratified epidermis in vivo. Efficient conversion of somatic cells into keratinocytes could have important implications for studying genetic skin diseases and designing regenerative therapies to ameliorate devastating skin conditions.COST (European Cooperation in Science and Technology) (EU-COST Action BM1302 “Joining Forces in Corneal Regeneration Research”)University of Cypru

The Evolutionarily Conserved Longevity Determinants HCF-1 and SIR-2.1/SIRT1 Collaborate to Regulate DAF-16/FOXO

The conserved DAF-16/FOXO transcription factors and SIR-2.1/SIRT1 deacetylases are critical for diverse biological processes, particularly longevity and stress response; and complex regulation of DAF-16/FOXO by SIR-2.1/SIRT1 is central to appropriate biological outcomes. Caenorhabditis elegans Host Cell Factor 1 (HCF-1) is a longevity determinant previously shown to act as a co-repressor of DAF-16. We report here that HCF-1 represents an integral player in the regulatory loop linking SIR-2.1/SIRT1 and DAF-16/FOXO in both worms and mammals. Genetic analyses showed that hcf-1 acts downstream of sir-2.1 to influence lifespan and oxidative stress response in C. elegans. Gene expression profiling revealed a striking 80% overlap between the DAF-16 target genes responsive to hcf-1 mutation and sir-2.1 overexpression. Subsequent GO-term analyses of HCF-1 and SIR-2.1-coregulated DAF-16 targets suggested that HCF-1 and SIR-2.1 together regulate specific aspects of DAF-16-mediated transcription particularly important for aging and stress responses. Analogous to its role in regulating DAF-16/SIR-2.1 target genes in C. elegans, the mammalian HCF-1 also repressed the expression of several FOXO/SIRT1 target genes. Protein–protein association studies demonstrated that SIR-2.1/SIRT1 and HCF-1 form protein complexes in worms and mammalian cells, highlighting the conservation of their regulatory relationship. Our findings uncover a conserved interaction between the key longevity determinants SIR-2.1/SIRT1 and HCF-1, and they provide new insights into the complex regulation of FOXO proteins

Caenorhabditis elegans HCF-1 Functions in Longevity Maintenance as a DAF-16 Regulator

The transcription factor DAF-16/forkhead box O (FOXO) is a critical longevity determinant in diverse organisms, however the molecular basis of how its transcriptional activity is regulated remains largely unknown. We report that the Caenorhabditis elegans homolog of host cell factor 1 (HCF-1) represents a new longevity modulator and functions as a negative regulator of DAF-16. In C. elegans, hcf-1 inactivation caused a daf-16-dependent lifespan extension of up to 40% and heightened resistance to specific stress stimuli. HCF-1 showed ubiquitous nuclear localization and physically associated with DAF-16. Furthermore, loss of hcf-1 resulted in elevated DAF-16 recruitment to the promoters of its target genes and altered expression of a subset of DAF-16-regulated genes. We propose that HCF-1 modulates C. elegans longevity and stress response by forming a complex with DAF-16 and limiting a fraction of DAF-16 from accessing its target gene promoters, and thereby regulates DAF-16-mediated transcription of selective target genes. As HCF-1 is highly conserved, our findings have important implications for aging and FOXO regulation in mammals

Regulation of Histone Deposition Proteins Asf1/Hir1 by Multiple DNA Damage Checkpoint Kinases in Saccharomyces cerevisiae

CAF-1, Hir proteins, and Asf1 are histone H3/H4 binding proteins important for chromatin-mediated transcriptional silencing. We explored genetic and physical interactions between these proteins and S-phase/DNA damage checkpoint kinases in the budding yeast Saccharomyces cerevisiae. Although cells lacking checkpoint kinase Mec1 do not display defects in telomeric gene silencing, silencing was dramatically reduced in cells lacking both Mec1 and the Cac1 subunit of CAF-1. Silencing was restored in cac1Δ and cac1Δ mec1Δ cells upon deletion of Rad53, the kinase downstream of Mec1. Restoration of silencing to cac1Δ cells required both Hir1 and Asf1, suggesting that Mec1 counteracts functional sequestration of the Asf1/Hir1 complex by Rad53. Consistent with this idea, the degree of suppression of silencing defects by rad53 alleles correlated with effects on Asf1 binding. Furthermore, deletion of the Dun1 kinase, a downstream target of Rad53, also suppressed the silencing defects of cac1Δ cells and reduced the levels of Asf1 associated with Rad53 in vivo. Loss of Mec1 and Rad53 did not alter telomere lengths or Asf1 protein levels, nuclear localization, or chromosome association. We conclude that the Mec1 and Dun1 checkpoint kinases regulate the Asf1-Rad53 interaction and therefore affect the activity of the Asf1/Hir complex in vivo

A critical examination of the principal theories of the Hebrew verbal system between 1827 and 1954 with particular reference to the waw consecutive problem

SIGLEAvailable from British Library Document Supply Centre- DSC:D42136/82 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

The response to 5-FU treatment can be captured with the combined Gompertz/two-compartment pharmacokinetic model: Indicative figures from two treated mice, one from each treatment group.

<p>Left panel–CM.41 from 5-FU 1; Right panel–CM.43 from 5-FU 2. The black squares indicate the measured tumor volumes while the green line is the fitted model based on Eqs (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143840#pone.0143840.e002" target="_blank">2</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143840#pone.0143840.e005" target="_blank">5</a>). The red dashed line is the prediction of what would have happened if the tumor was left untreated based on the pre-treatment data estimates of the tumor growth rate. Our model appears to accurately capture, both the growth and treatment dynamics of the tumor. The NMSE values for the three tumors of CM.41 are 44.7%, 26.8% and 35.4% and for the three tumors of CM.43 these are 18.5%, 6.7% and 13.0% respectively.</p

The variability of tumor growth <i>in vivo</i> can be captured with the Gompertz model: Indicative growth curves for a mouse with fast growing tumors (CM.37 –Left panel) and another with slow growing tumors (CM.53 –Right panel).

<p>The mice belong to the DMSO group and received no drug treatment. The black squares are the measured tumor volumes and the red line is the fitted model output using Eq (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143840#pone.0143840.e002" target="_blank">2</a>) without treatment. The model provides an overall satisfactory fit to the data. The NMSE values are 17.4%, 5.3%, 10.7% for the three tumors of CM.37 and 16.1%, 27.1%, 19.8% for the three tumors of CM.53. Additionally tumor growth rate appears to be mouse specific.</p

Experimental design and pharmacokinetic model: A. Schematic outline of the experiment. B. Plasma (<i>C</i>_<i>1</i>) and tumor site (<i>C</i>_<i>2</i>) drug concentrations for the two 5-FU dosages administered in the experiment.

<p>The figures show the concentrations from the time when the drug was administered until 24 hours later and are calculated according to Eq (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143840#pone.0143840.e005" target="_blank">5</a>).</p