Yu Y et al. (2000) Mol Cell Biol "Architectural transcription factors and the SAGA complex function in parallel pathways to activate transcription."

Yu Y, Eriksson P, Stillman DJ

[Mol Cell Biol, 2000]

Recent work has shown that transcription of the yeast HO gene involves the sequential recruitment of a series of transcription factors. We have performed a functional analysis of HO regulation by determining the ability of mutations in SIN1, SIN3, RPD3, and SIN4 negative regulators to permit HO expression in the absence of certain activators. Mutations in the SIN1 (=SPT2) gene do not affect HO regulation, in contrast to results of other studies using an HO:lacZ reporter, and our data show that the regulatory properties of an HO:lacZ reporter differ from that of the native HO gene. Mutations in SIN3 and RPD3, which encode components of a histone deacetylase complex, show the same pattern of genetic suppression, and this suppression pattern differs from that seen in a sin4 mutant. The Sin4 protein is present in two transcriptional regulatory complexes, the RNA polymerase II holoenzyme/mediator and the SAGA histone acetylase complex. Our genetic analysis allows us to conclude that Swi/Snf chromatin remodeling complex has multiple roles in HO activation, and the data suggest that the ability of the SBF transcription factor to bind to the HO promoter may be affected by the acetylation state of the HO promoter. We also demonstrate that the Nhp6 architectural transcription factor, encoded by the redundant NHP6A and NHP6B genes, is required for HO expression. Suppression analysis with sin3, rpd3, and sin4 mutations suggests that Nhp6 and Gcn5 have similar functions. A gcn5 nhp6a nhp6b triple mutant is extremely sick, suggesting that the SAGA complex and the Nhp6 architectural transcription factors function in parallel pathways to activate transcription. We find that disruption of SIN4 allows this strain to grow at a reasonable rate, indicating a critical role for Sin4 in detecting structural changes in chromatin mediated by Gcn5 and Nhp6. These studies underscore the critical role of chromatin structure in regulating HO gene expression.

Fu X et al. (2015) Biochem Biophys Res Commun "An oxidative fluctuation hypothesis of aging generated by imaging HO levels in live Caenorhabditis elegans with altered lifespans."

Dickinson BC, Chang Z, Chang CJ, Tang Y, Fu X

[Biochem Biophys Res Commun, 2015]

Reactive oxygen species (ROS) are important factors mediating aging according to the free radical theory of aging. Few studies have systematically measured ROS levels in relationship to aging, partly due to the lack of tools for detection of specific ROS in live animals. By using the HO-specific fluorescence probe Peroxy Orange 1, we assayed the HO levels of live Caenorhabditis elegans with 41 aging-related genes being individually knocked down by RNAi. Knockdown of 14 genes extends the lifespan but increases HO level or shortens the lifespan but decreases HO level, contradicting the free radical theory of aging. Strikingly, a significant inverse correlation between lifespan and the normalized standard deviation of HO levels was observed (p < 0.0001). Such inverse correlation was also observed in worms cultured under heat shock conditions. An oxidative fluctuation hypothesis of aging is thus proposed and suggests that the ability of animals to homeostatically maintain the ROS levels within a narrow range is more important for lifespan extension than just minimizing the ROS levels though the latter still being crucial.

Loboda A et al. (2016) Cell Mol Life Sci "Role of Nrf2/HO-1 system in development, oxidative stress response and diseases: an evolutionarily conserved mechanism."

Damulewicz M, Dulak J, Jozkowicz A, Loboda A, Pyza E

[Cell Mol Life Sci, 2016]

The multifunctional regulator nuclear factor erythroid 2-related factor (Nrf2) is considered not only as a cytoprotective factor regulating the expression of genes coding for anti-oxidant, anti-inflammatory and detoxifying proteins, but it is also a powerful modulator of species longevity. The vertebrate Nrf2 belongs to Cap 'n' Collar (Cnc) bZIP family of transcription factors and shares a high homology with SKN-1 from Caenorhabditis elegans or CncC found in Drosophila melanogaster. The major characteristics of Nrf2 are to some extent mimicked by Nrf2-dependent genes and their proteins including heme oxygenase-1 (HO-1), which besides removing toxic heme, produces biliverdin, iron ions and carbon monoxide. HO-1 and their products exert beneficial effects through the protection against oxidative injury, regulation of apoptosis, modulation of inflammation as well as contribution to angiogenesis. On the other hand, the disturbances in the proper HO-1 level are associated with the pathogenesis of some age-dependent disorders, including neurodegeneration, cancer or macular degeneration. This review summarizes our knowledge about Nrf2 and HO-1 across different phyla suggesting their conservative role as stress-protective and anti-aging factors.

Abate JP et al. (2009) Cell Metab "Life is short, if sweet."

Blackwell TK, Abate JP

[Cell Metab, 2009]

Insulin is essential for glucose homeostasis, but reducing its activity delays the aging process in model organisms. In this issue of Cell Metabolism, Lee et al. (2009) show how these effects of insulin signaling intersect when glucose is fed to C. elegans.

Zheng, Chaogu et al. (2019) International Worm Meeting "F-box protein MEC-15 promotes microtubule stability and neurite growth by antagonizing the activity of HSP90 chaperone network."

Jao, Susan Laura Javier, Chalfie, Martin, Atlas, Emily, Sayegh, Natalie Yvonne, Lee, Ho Ming Terence, Hall, David H., Nguyen, Ken C. Q., Zheng, Chaogu

[International Worm Meeting, 2019]

Microtubule (MT) stability plays an important role in regulating neurite growth. We previously found that neomorphic (neo) gain-of-function mutations of mec-7/b-tubulin led to increased MT stability and the growth of an ectopic, posteriorly directed neurite in the anterior touch receptor neuron (TRN) ALMs. This clear phenotype provided a sensitized background for identifying novel MT regulators. Through a suppressor screen, we identified a loss-of-function (lf) mutation in mec-15, which suppressed the growth of ALM posterior neurite (ALM-PN) in mec-7(neo) mutants. mec-15 encodes a F-box protein with four WD40 repeats. Rescue experiments showed that mec-15 functions cell autonomously in ALMs and its function requires the F-box. mec-15(lf) single mutants showed the shortening of both PLM anterior and posterior neurites and PLM branching defects, suggesting that MEC-15 is required not only for the growth of ectopic ALM neurites but also for the normal development of TRN morphology. Because MEC-15 physically interacts with SKR-1/Skp1, and TRN-specific RNAi against uba-1 (ubiquitin-activating enzyme) suppressed the generation of ALM-PN in mec-7(neo) mutants, a SCF complex-mediated ubiquitination pathway promotes MT stability and neurite development. To understand the downstream target of MEC-15, we took mec-7(neo); mec-15(lf) as the starter strain and carried out another suppressor screen searching for mutants with recovered ALM-PN. We identified one sti-1(lf), four pph-5(lf), and two dlk-1(lf) alleles in the screen. STI-1/Hop is a cochaperone that physically links Hsp70 and Hsp90 via the tetratricopeptide repeat (TPR)-domain, and the phosphatase PPH-5 is a TPR-containing Hsp90 cofactor. Through a candidate-based approach, we found that similar to mutations in sti-1 and pph-5, the loss of hsp-90, hsp-110/Hsp70, and daf-41/p23 also recovered the growth ALM-PN in mec-15(lf); mec-7(neo) double mutants and rescued the TRN developmental defects in mec-15(lf) single mutants. Electron microscopic studies found that the number of MTs in a cross-section of TRN neurite is dramatically decreased in mec-15(lf) mutants and this defect is rescued in mec-15; pph-5 or mec-15; sti-1 double mutants. Functionally, the reduced touch sensitivity of mec-15 mutants is restored in those double mutants. Thus, our data suggest that MEC-15 promotes MT stability and neuronal growth by inhibiting the Hsp90 chaperone network. One potential target of Hsp90 chaperone is DLK-1, the Dual-Leucine zipper Kinase, which was recently identified as a HSP90 client in mouse neurons. We found that dlk-1(lf) mutations suppressed the defects caused by the loss of mec-15 and overexpression of dlk-1 in the TRNs rescued the lack of Hsp90 chaperones, causing MT instability and neurite growth defects. Therefore, our results revealed an unexpected negative regulation of neurodevelopment by the molecular chaperones.

Lee C et al. (2017) Bio Protoc "Single-molecule RNA Fluorescence in situ Hybridization (smFISH) in Caenorhabditis elegans."

Sorensen EB, Lee C, Seidel HS, Lynch TR, Crittenden SL, Kimble J

[Bio Protoc, 2017]

Single-molecule RNA fluorescence <i>in situ</i> hybridization (smFISH) is a technique to visualize individual RNA molecules using multiple fluorescently-labeled oligonucleotide probes specific to the target RNA ( Raj <i>et al.</i>, 2008 ; Lee <i>et al.</i>, 2016a ). We adapted this technique to visualize RNAs in the <i>C. elegans</i> whole adult worm or its germline, which enabled simultaneous recording of nascent transcripts at active transcription sites and mature mRNAs in the cytoplasm ( Lee <i>et al.</i>, 2013 and 2016b). Here we describe each step of the smFISH procedure, reagents, and microscope settings optimized for <i>C. elegans</i> extruded gonads.

Dawes-Hoang RE et al. (2003) Dev Cell "Bringing classical embryology to C elegans gastrulation."

Zallen JA, Wieschaus EF, Dawes-Hoang RE

[Dev Cell, 2003]

In a recent paper, Lee and Goldstein develop an explant assay that recapitulates key aspects of gastrulation in C. elegans and permits classical embryological manipulations. The resulting detailed analysis of cell behavior will ultimately extend to broader issues, such as, whether morphogenesis can be described as the sum of single-cell events or if unique phenomena emerge at the multicellular level.

Bauer, Jack et al. (2021) MicroPubl Biol

Labb, Jean-Claude, Lacroix, La, Bauer, Jack

[MicroPubl Biol, 2021]

To perturb actomyosin function in the primordial germ line, we first monitored germ line organization in L1-stage animals bearing temperature-sensitive (ts) alleles in genes encoding actomyosin regulators and that were reported to interfere with cytokinesis during embryogenesis (Davies et al. 2014). Previous work demonstrated that the initial stages of germline expansion occur normally in cyk-4(ts) and zen-4(ts) animals raised at restrictive temperature from the L1 stage (Lee et al. 2018). We found that primordial germ line organization in cyk-1(ts), nmy-2(ts), cyk-4(ts) or zen-4(ts) L1 larvae maintained at restrictive temperature for 12h was no different than control (Figure 1A-B). Furthermore, the first primordial germ cell (PGC) division occurred normally upon feeding these animals at restrictive temperature with typical bacterial food (E. coli OP50). As noted previously (Lee et al. 2018), germ line disorganization and sterility were observed in all cases when animals reached adulthood (Figure 1B).

Mondol V et al. (2012) Curr Top Dev Biol "Let's make it happen: the role of let-7 microRNA in development."

Mondol V, Pasquinelli AE

[Curr Top Dev Biol, 2012]

Noncoding RNAs have emerged as an integral part of posttranscriptional gene regulation. Among that class of RNAs are the microRNAs (miRNAs), which posttranscriptionally regulate target mRNAs containing complementary sequences. The broad presence of miRNAs in lower eukaryotes, plants, and mammals highlights their importance throughout evolution. MiRNAs have been shown to regulate many pathways, including development, and disruption of miRNA function can lead to disease (Ivey and Srivastava, 2010; Jiang et al., 2009). Although the first miRNA genes were discovered in the nematode, Caenorhabditis elegans, almost 20 years ago, the field of miRNA research began when they were found in multiple organisms a little over a decade ago (Lagos-Quintana et al., 2001; Lau et al., 2001; Lee and Ambros, 2001; Lee et al., 1993; Pasquinelli et al., 2000; Wightman et al., 1993). Here, we review one of the first characterized miRNAs, let-7, and describe its role in development and the intricacies of its biogenesis and function.

Way JC et al. (1994) Bioessays "Cell polarity and the mechanism of asymmetric cell division."

Hung M-S, Run JQ, Way JC, Wang LL

[Bioessays, 1994]

During development, one mechanism for generating different cell types is asymmetric cell division, by which a cell divides and contributes different factors to each of its daughter cells. Asymmetric cell division occurs throughout the eukaryotic kingdom, from yeast to humans. Many asymmetric cell divisions occur in a defined orientation. This implies a cellular mechanism for sensing direction, which must ultimately lead to differences in gene expression between two daughter cells. In this review, we describe two classes of molecules: regulatory factors that are differentially expressed upon asymmetric cell division, and components of a signal transduction pathway that may define cell polarity. The lin-11 and mec-3 genes of C. elegans, the Isl-1 gene of mammals and the HO gene of yeast, encode regulatory factors that determine cell type of one daughter after asymmetric cell division. The CDC24 and CDC42 genes of yeast affect both bud positioning and orientation of mating projections, and thus may define a general cellular polarity. We speculate that molecules such as Cdc24 and Cdc42 may regulate expression of genes such as lin-11, mec-3, Isl-1 and HO upon asymmetric cell division.