In mammalian cells, products of the INK4a-ARF locus play major roles in senescence and tumour suppression in different contexts, whereas the adjacent INK4b gene is more generally associated with transforming growth factor beta (TGF-beta)-mediated growth arrest. As the chicken genome does not encode an equivalent of INK4a, we asked whether INK4b and/or ARF contribute to replicative senescence in chicken cells.
The nicotinamide adenine dinucleotide (NAD)-dependent deacetylase Sir2 (silent information regulator 2) regulates gene silencing in yeast and promotes lifespan extension during caloric restriction. The mammalian homologue of Sir2 (SirT1) regulates p53, NF-kappaB and Forkhead transcription factors, and is implicated in stress response. This report shows that the cell-cycle and apoptosis regulator E2F1 induces SirT1 expression at the transcriptional level. Furthermore, SirT1 binds to E2F1 and inhibits E2F1 activities, forming a negative feedback loop.
This past decade has seen the identification of numerous conserved genes that extend lifespan in diverse species, yet the number of compounds that extend lifespan is relatively small. A class of compounds called STACs, which were identified as activators of Sir2/SIRT1 NAD+-dependent deacetylases, extend the lifespans of multiple species in a Sir2-dependent manner and can delay the onset of age-related diseases such as cancer, diabetes and neurodegeneration in model organisms.
XPF-ERCC1 endonuclease is required for repair of helix-distorting DNA lesions and cytotoxic DNA interstrand crosslinks. Mild mutations in XPF cause the cancer-prone syndrome xeroderma pigmentosum. A patient presented with a severe XPF mutation leading to profound crosslink sensitivity and dramatic progeroid symptoms. It is not known how unrepaired DNA damage accelerates ageing or its relevance to natural ageing. Here we show a highly significant correlation between the liver transcriptome of old mice and a mouse model of this progeroid syndrome.
Granulocyte macrophage colony-stimulating factor (GM-CSF) is a key cytokine for the generation and stimulation of dendritic cells (DCs), and it may also play a pivotal role in promoting the survival of DCs. In this study, the feasibility of creating a cancer vaccine using DCs adenovirally transduced with the carcinoembryonic antigen (CEA) gene and the GM-CSF gene was examined. In addition, the effect of the co-transduction of GM-CSF gene on the lifespan of these genetically modified DCs was determined.
FKHRL1 is one of the human homologues of DAF-16, which is concerned with longevity in Caenorhabditis elegans. Previously, we demonstrated that FKHRL1 functions downstream of Akt in erythropoietin (EPO) signaling and that it is directly phosphorylated by activated Akt. Because phosphorylated FKHRL1 loses its transcriptional activity and translocates into the cytoplasm, FKHRL1 appears to be nonfunctional in the presence of EPO.
Human papillomaviruses (HPVs) belonging to the Betapapillomavirus genus have recently been implicated in squamous cell carcinomas of the skin, though the mechanisms by which they initiate carcinogenesis are unclear. We show that human foreskin keratinocytes (HFKs) expressing several betapapillomavirus E6 (beta-E6) proteins display life span extension, but not to the extent seen in HFKs expressing HPV type 16 E6 (16E6). Additionally, we demonstrate that beta-E6 proteins can differentially activate telomerase.
Proceedings of the National Academy of Sciences of the United States of America
The burden of protein misfolding is believed to contribute to aging. However, the links between adaptations to conditions associated with protein misfolding and resistance to the time-dependent attrition of cellular function remain poorly understood. We report that worms lacking aip-1, a homologue of mammalian AIRAP (arsenic-inducible proteasomal 19S regulatory particle-associated protein), are not only impaired in their ability to resist exposure to arsenite but also exhibit shortened lifespan and hypersensitivity to misfolding-prone proteins under normal laboratory conditions.
Proteasome-dependent degradation has been extensively investigated and has been shown to play a vital role in the maintenance of cellular homeostasis. Proteasome activity and expression are reduced during aging and replicative senescence. Its activation has been shown to confer lifespan extension in human diploid fibroblasts (HDFs), whereas partial proteasome inhibition triggers an irreversible premature senescent state in young HDFs.
Calorie restriction (CR) produces several health benefits and increases lifespan in many species. Studies suggest that alternate-day fasting (ADF) and exercise can also provide these benefits. Whether CR results in lifespan extension in humans is not known and a direct investigation is not feasible. However, phenotypes observed in CR animals when compared to ad libitum fed (AL) animals, including increased stress resistance and changes in protein expression, can be simulated in cells cultured with media supplemented with blood serum from CR and AL animals.