Molecular characterization ofnumr-1andnumr-2: genes that increase both resistance to metal-induced stress and lifespan inCaenorhabditis elegans

Abstract

SummaryTo define the mechanisms involved in the molecular response to the carcinogenic metal cadmium, two novel metal-inducible genes from C. elegans were characterized: numr-1 and numr-2 (nuclear localized metal responsive). numr-1 and numr-2 sequences and cellular patterns of expression are identical, indicating that these are functionally equivalent genes. Constitutive transcription of numr-1 and numr-2 is developmentally regulated and occurs in the intestine, in head and tail neurons, and vulva muscles. Exposure to metals induces numr-1 and numr-2 transcription in pharyngeal and intestinal cells. Other environmental stressors do not affect transcription, indicating that these are metal-specific, stress-responsive genes. NUMR-1 and NUMR-2 target to nuclei and colocalize with HSF-1, suggesting that they may be components of nuclear stress granules. Nematodes overexpressing NUMR-1 and NUMR-2 are resistant to stress and live longer than control animals; likewise reducing expression increases sensitivity to metals and decreases neuromuscular functions. Upstream regulatory regions of both genes contain potential binding sites for DAF-16 and SKN-1, which are components of the insulin-IGF-like signaling pathway. This pathway regulates longevity and stress responses in C. elegans. NUMR-1 and NUMR-2 may function to promote resistance to environmental stressors and longevity, which is mediated by the insulin-IGF-like signaling pathway.Key words: C. elegans, Cadmium, Stress response, Lifespan, LongevityJournal of Cell Science increase in the steady-state mRNA level following a 24-hour cadmium exposure (Cui et al., 2007). A second C. elegans gene, originally designated F08F8.1, was subsequently identified based on sequence identity. These genes are now designated numr-1 and numr-2 (nuclear localized metal responsive), respectively.In the present report, the genomic organization, in vivo cellular patterns of expression, effects of transition metals and other stressors on transcription, and phenotypes associated with increased and decreased expression of numr-1 and numr-2 are presented. Phenotypes associated with these genes include changes in neuromuscular activities, as well as increased resistance to metal toxicity and increased lifespan. Results Sequence analysis of numr-1 and numr-2numr-1 and numr-2 were located less than 1 kb apart in a divergent orientation on chromosome III (Fig. 1). numr-1 mRNA was predicted to be encoded by a single exon. By contrast, numr-2 mRNA was predicted to be encoded by five exons, the first of which was ~99% identical to the numr-1 exon. Sequences of the full-length mRNAs and the exon arrangement for numr-1 and numr-2 were determined using 3Ј-and 5Ј-RACE. The sequence of the 3Ј-end of numr-1 was consistent with that reported in WormBase (version WS201). Using 3Ј RACE, however, cDNAs from predicted exons 2-5 of numr-2 were not isolated. This suggested that numr-2 was annotated incorrectly and that it also was a single exon gene. Sequences for the 5Ј-ends of numr-1 and numr-2 were 100% iden...

Distinct transcriptomic responses of Caenorhabditis elegans to pristine and sulfidized silver nanoparticles

“…and its response to pristine Ag-MNP and AgNO3 is indicative that some of the effects are also due to dissolved ions (Tvermoes et al, 2010). Our previous study showed that the dissolved Ag released from sAg-MNP (0.43%) over 24 hr is more than 13 times lower than from pristine Ag-MNP (5.8%) (Starnes et al, 2015), which would explain why we did not observe up-regulation in numr-1 expression in response to sAg-MNP .…”

“…The fourth gene, nuclear metal responsive gene (numr-1), is shared between Ag-MNP and AgNO3 and was up-regulated in both exposures, but showed no effect in sAg-MNP exposure. Numr-1 is a nuclear localized metal response gene and therefore should be closely related due to toxicity from metal ion exposure (Tvermoes et al, 2010).…”

Anti-aging effects of deuterium depletion on Mn-induced toxicity in a C. elegans model

“…As DAF-16 migration from the cytosol to the mitochondria is essential for the activation and expression of antioxidant enzymes, such as SOD, the absence of this transcription factor likely generates an imbalance in the pro-oxidant/antioxidant homeostasis, causing increased ROS production, mitochondrial dysfunction, cell death and, consequently, shorter life-span. Reinforcing this hypothesis, pro-oxidant agents such as paraquat and cadmium reduce life-span as well as DAF-16 protein levels (Guan et al, 2010; Tvermoes et al, 2010). In order to determine which step in the DAF-16 cascade was negatively modulated by Mn, we analyzed the levels of the insulin-like receptor DAF-2; the levels of the intermediary kinase AKT; and also a DAF-16 target, SOD-3, a mitochondrial iron/manganese-dependent antioxidant enzyme.…”

Longevity and stress in Caenorhabditis elegans

“…The mechanism behind heavy-metal toxicity is not well understood, but it is thought that heavy-metal ions cause damage to the cell by inactivating and denaturing proteins, and by promoting the formation of reactive oxygen species [67-69]. The thiol tripeptide glutathione, a class of cysteine-rich proteins called metallothioneins, and other larger metal-binding proteins protect the cell from heavy-metal stress by chelating and sequestering metal ions [67, 69, 70]. Heavy-metal stress also activates the expression of cell repair mechanisms, including heat-shock proteins [70].…”