During neuronal development, β-actin serves an important role in growth cone mediated axon guidance. Consistent with this notion, in vivo ablation of the β-actin gene leads to abnormalities in the nervous system. However, whether β-actin is involved in the regulation of neuronal gene programs is not known. In this study, we directly reprogramed β-actin+/+ WT, β-actin+/- HET and β-actin-/- KO mouse embryonic fibroblast (MEFs) into chemically induced neurons (CiNeurons). Using RNA-seq analysis, we profiled the transcriptome changes among the CiNeurons. We discovered that induction of neuronal gene programs was impaired in KO CiNeurons in comparison to WT ones, whereas HET CiNeurons showed an intermediate levels of induction. ChIP-seq analysis of heterochromatin markers demonstrated that the impaired expression of neuronal gene programs correlated with the elevated H3K9 and H3K27 methylation levels at gene loci in β-actin deficient MEFs, which is linked to the loss of chromatin association of the BAF complex ATPase subunit Brg1. Together, our study shows that heterochromatin alteration in β-actin null MEFs impedes the induction of neuronal gene programs during direct reprograming. These findings are in line with the notion that H3K9Me3-based heterochromatin forms a major epigenetic barrier during cell fate change.

In humans, the cytosolic glutathione S-transferase (GST) family of proteins is encoded by 16 genes presented in seven different classes. GSTs exhibit remarkable structural similarity with some overlapping functionalities. As a primary function, GSTs play a putative role in Phase II metabolism by protecting living cells against a wide variety of toxic molecules by conjugating them with the tripeptide glutathione. This conjugation reaction is extended to forming redox sensitive post-translational modifications on proteins: S-glutathionylation. Apart from these catalytic functions, specific GSTs are involved in the regulation of stress-induced signaling pathways that govern cell proliferation and apoptosis. Recently, studies on the effects of GST genetic polymorphisms on COVID-19 disease development revealed that the individuals with higher numbers of risk-associated genotypes showed higher risk of COVID-19 prevalence and severity. Furthermore, overexpression of GSTs in many tumors is frequently associated with drug resistance phenotypes. These functional properties make these proteins promising targets for therapeutics, and a number of GST inhibitors have progressed in clinical trials for the treatment of cancer and other diseases.

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Cytosolic glutathione transferases (GSTs) comprise a large family of enzymes with canonical structures that diverge functionally and structurally among mammals, invertebrates and plants. Whereas mammalian GSTs have been characterized extensively with regard to their structure and function, invertebrate GSTs remain relatively unstudied. The invertebrate GSTs do, however, represent potentially important drug targets for infectious diseases and agricultural applications. In addition, it is essential to fully understand the structure and function of invertebrate GSTs, which play important roles in basic biological processes. Invertebrates harbor delta- and epsilon-class GSTs, which are not found in other organisms.Drosophila melanogasterGSTs (DmGSTs) are likely to contribute to detoxication or antioxidative stress during development, but they have not been fully characterized. Here, the structures of two epsilon-class GSTs fromDrosophila, DmGSTE6 and DmGSTE7, are reported at 2.1 and 1.5 Å resolution, respectively, and are compared with other GSTs to identify structural features that might correlate with their biological functions. The structures of DmGSTE6 and DmGSTE7 are remarkably similar; the structures do not reveal obvious sources of the minor functional differences that have been observed. The main structural difference between the epsilon- and delta-class GSTs is the longer helix (A8) at the C-termini of the epsilon-class enzymes.

Summary 26 The explosive 2,4,6-trinitrotoluene (TNT) is a significant, global environmental 27 pollutant that is both toxic and recalcitrant to degradation. Given the sheer scale, and 28 inaccessible nature of contaminated areas, phytoremediation may be a viable clean-up 29 approach. Here, we have characterised a Drosophila melanogaster (Meigen, 1830) 30 glutathione transferase (DmGSTE6) which has activity towards TNT. 31  Recombinantly-expressed, purified DmGSTE6 produces predominantly 2-32 glutathionyl-4,6-dinitrotoluene, and has a 2.5-fold higher V max , and 5-fold lower K m 33 than previously characterised TNT-active Arabidopsis thaliana (L. 2004), and many contaminated sites in Europe and Asia (Kalderis et al., 2011; Pichtel, 2012). 59)For example, the Werk Tanne former ammunition site in Germany, detonated in 1944, is 60 heavily contaminated with TNT (Eisentraeger et al., 2007). Increased environmental 61 awareness is now compelling governments to identify sites of explosives contamination and 62 put together remediation strategies (Lima et al., 2011). However, a major challenge to 63 cleaning-up these sites is the sheer scale and hazardous nature of many contaminated sites, 64 which rules-out many strategies such as excavation, land fill and off-site treatments, as 65 prohibitively expensive. Phytoremediation may be a viable alternative approach. 66TNT is not readily degraded in the environment due to the electron-withdrawing properties of 67 the three nitro groups of TNT which render the aromatic ring particularly resistant to 68 oxidative attack and ring cleavage (Qasim et al., 2009); the main route of aromatic 69 compounds by soil microbes. Instead microbial flora catalyse a series of reductive reactions, 70 producing predominantly hydroxylamino dinitrotoluene (HADNT) and amino dinitrotoluene 71 (ADNT) and further reduced derivatives (Rylott et al., 2011b). In plants, HADNT and ADNT 72 can be conjugated to sugars, for example, to glucose by UDP-glucosyltransferases (Gandia-73 Herrero et al., 2008), and it has recently been shown that glutathione transferases can 74 conjugate the TNT molecule directly (Gunning et al., 2014; Rylott et al., 2015). Two 75Arabidopsis thaliana (L.) Heynh (Arabidopsis) glutathione transferase (GST) genes, AtGST-76 U24 and AtGST-U25, are specifically upregulated in response to TNT exposure, and their 77 gene products catalyse the formation of three characterised TNT glutathionyl-products 78 (Gunning et al., 2014). The removal of a nitro group in one of the three products, 2-79 glutathionyl-4,6-dinitrotoluene, has the potential to be more amenable to subsequent 80 biodegradation in the environment, a property that could be applied in planta for the 81 5 detoxification of TNT in the field. Expression of AtGST-U24 and AtGST-U25 in Arabidopsis 82 conferred increased ability to take up and detoxify TNT; however, in the absence of TNT, 83 overexpression of these GSTs caused a reduction in plant biomass; an effect with deleterious 84 implications for xenobiotic detoxification...