Aminoallyl-UTP Supplier The authors would like to thank

The authors would like to thank Felecia Codrea and Jessica Scholes of the UCLA BSCRC FACS core, Suhua Feng of the UCLA BSCRC Sequencing core, and Tiasha Shafiq for immunostaining. This project was funded by NIH grant P01HD075795. Time-mated breeding was supported by NIH OD P51OD011092 (J.D.H.). The Laboratory of Developmental Biology, University of Washington, Seattle is supported by NIH Award Number 5R24HD000836 from the NICHD. W.L. is supported by a Philip J. Whitcome fellowship from the Molecular Biology Institute of University of California, Los Angeles, and a scholarship from the Chinese Scholarship Council. DC is supported by a Postdoctoral Fellowship from the UCLA BSCRC and the Shaffer Family Foundation. Human conceptus tissue requests can be made to: [email protected].
Introduction The tight regulation of reactive oxygen species (ROS) levels is crucial in maintaining cellular homeostasis. While the metabolic processes of a cell generate ROS such as superoxide anions and hydroxyl free radicals, their levels are kept at a low-to-moderate range which is essential for cellular proliferation, differentiation, and survival (Trachootham et al., 2009). ROS levels are modulated by a balance between pro-oxidants and antioxidants. When increased ROS are not countered by antioxidant activity or reducing equivalents, a cell is said to be in the state of oxidative stress. High levels of ROS can damage DNA, proteins, and lipids. As such, oxidative stress is linked to the pathogenesis of human diseases such as neurodegenerative disorders and cancer (Floyd and Hensley, 2002; Barnham et al., 2004; Khandrika et al., 2009; Rios-Arrabal et al., 2013). Hence, understanding the molecular mechanisms underlying the redox Aminoallyl-UTP Supplier and characterizing the effects of ROS on cellular homeostasis may lead to the development of effective therapeutic interventions for the treatment of ROS-associated human diseases. In mammals, Keap1 (Kelch-like ECH-associated protein 1)/Nrf2 (NF-E2-related factor 2) signaling plays important roles in the regulation of ROS levels. Nrf2 functions in the antioxidant response element (ARE)-dependent transcriptional regulation of antioxidant and detoxification genes (Itoh et al., 1997, 1999a, 1999b). In the absence of oxidative stress, Nrf2 is bound to its cytoplasmic inhibitor Keap1 and prevented from translocating into the nucleus. Keap1 subsequently promotes the 26S proteosomal degradation of Nrf2 via a Cul3-based E3 ligase, negatively regulating ARE-mediated gene expression (McMahon et al., 2003; Kobayashi et al., 2004). In the presence of electrophilic and oxidative stress, reactive cysteine residues present on Keap1 are covalently modified, preventing the Keap1/Cul3 E3 ubiquitin ligase-mediated proteosomal degradation of Nrf2 (Kobayashi et al., 2004). Thus, Keap1 functions as a sensor of electrophilic and oxidative stress, and controls the release of Nrf2. Nrf2 then translocates into the nucleus, heterodimerizes with Maf, and binds to the ARE sequence located at the promoter region of its target genes (Motohashi et al., 2002). Binding of the Nrf2/Maf dimer to the multiple ARE sequences promotes the expression of an array of antioxidant and detoxification enzymes, which act to counter oxidative stress by scavenging ROS. In Drosophila, the Keap1/Nrf2 signaling pathway was also shown to play roles in the regulation of oxidative stress tolerance, lifespan, and xenobiotic responses (Sykiotis and Bohmann, 2008; Misra et al., 2011). Keap1/Nrf2 signaling becomes activated by oxidant agents such as paraquat, followed by the induction of antioxidant and detoxification responses (Nguyen et al., 2009). CncC (cap \'n\' collar isoform C) is the Drosophila homolog of Nrf2 and is known to regulate the ARE-mediated transcription of antioxidant genes (Sykiotis and Bohmann, 2008, 2010). These findings suggest that Keap1/Nrf2 signaling is evolutionarily conserved across phyla.