**Author details**

located between −356 and −330 from the transcription start site and targeted by Nrf2, has been identified in SOD1 promoter [40]. By means of a probe harbouring the SOD1 ARE element, we reported the presence of a dynamic protein-DNA complex, which suggested that after H2O2 treatment, the cis-acting ARE sequence in SOD1 promoter plays an important role by recruiting multiple TFs and/or cofactors, probably co-operating to modulate SOD1 mRNA induction under oxidative stress. ChIP assay followed by qRT-PCR with primers designed to flank the ARE element in SOD1 promoter showed that Nrf2 occupancy at the ARE elements in SOD1 promoter did not change after H2O2 treatment. We also reported a minimal increased associ‐ ation at the ARE element in NQO1 gene, a well-known Nrf2 gene target, thus indicating that Nrf2 cannot gain access to SOD1 5′-flanking region in a native chromatin context. SOD1 mRNA up-regulation in response to H2O2 oxidative treatment might indeed be ascribed to the involvement of other transcriptional factors. These data suggested that SOD1 promoter is not a canonical downstream target of the Nrf2 regulatory network and that Nrf2 may act as a 'constitutive' TF, binding to SOD1 ARE sequence even without stimulus, while H2O2 treatment could induce changes in the chromatin conformation with consequent changes in the rela‐ tionship between the different TFs. In regard to SOD1 gene, it has been wrongly considered a housekeeping gene; however, its inducible transcription is finely regulated by *cis*-acting

Until now, post-transcriptional control mechanisms of SOD1 expression are still unexplored; nevertheless, post-transcriptional control represents a specific and punctual regulatory mechanism for gene expression which can easily modify protein levels in response to extrac‐ ellular stimuli [41, 42]. Variations in gene expression are often the result of synergy between transcriptional and post-transcriptional regulatory mechanisms [28]. Very few data on posttranscriptional regulation of SOD1 have been reported so far. Two species of SOD1 mRNA with different 3′UTR lengths which produce *in vitro* different quantities of SOD1 protein have been identified. Kilk and colleagues [43] reported that the ability of long mRNA to produce more SOD1 enzyme seems to be related to specific sequences located in the 3′UTR; moreover, they identified the presence of AREs in this region (AUUUA, CUUUA, AUUUG, GUUUUA, AUUUU, and AUUUC). In general, AREs represent the docking sites for different RNAbinding proteins (RBPs), which can affect the metabolism of the target transcripts [44]. Among ARE-binding RBPs, ELAV (or Hu) proteins play a critical role [45]; ELAV family comprises the neuron-specific members HuB, HuC, and HuD [46] and the ubiquitously expressed HuR. ELAV proteins act primarily as positive regulators of gene expression; they can increase the stability and/or translation of target mRNAs whose proteins have fundamental cellular

Given the lack of data on this issue in ALS pathogenesis, Cereda's group [26] focused its attention on the modulation of SOD1 mRNA levels by post-transcriptional mechanisms, in particular via ELAV proteins. Considering that oxidative stress plays a critical role in sporadic ALS, and that it is a trigger of ELAV activation, by treating human neuroblastoma SH-SY5Y cells with 1 mM H2O2, a significant up-regulation of SOD1 mRNA levels was reported [47].

sequences and the corresponding transactive factors [39].

**3.2. Post-transcriptional regulation**

80 Update on Amyotrophic Lateral Sclerosis

functions.

Diamanti Luca1\*, Zucchi Elisabetta<sup>2</sup> , Pansarasa Orietta<sup>3</sup> , Ceroni Mauro1 and Cereda Crisitna<sup>3</sup>

\*Address all correspondence to: lukdiamonds@libero.it

1 Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy; 'C. Mondino' National Neurological Institute, Pavia, Italy

2 Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy

3 Laboratory of Experimental Neurobiology, 'C. Mondino' National Neurological Institute, Pavia, Italy

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