Oxidative stress causes damage to cells by creating reactive oxygen species (ROS), which are harmful molecules that destroy cellular structure and impair protein function. The overproduction of ROS is detrimental, having been linked to the onset of premature ageing and age-related diseases, such as Alzheimer's and Parkinson's. Our lab has previously found that a partial deletion of brap2 (BRCA-1 associated protein 2) significantly enhances nuclear localization of SKN-1 and increased the expression of
gst-4, a phase II detoxification enzyme. An RNAi screen for 940 transcription factors on a
brap-2;
gst-4::gfp strain resulted in more than 20 candidates that are proposed to alter expression of
gst-4 in BRAP-2/SKN-1/ROS detoxification pathway. One of those genes,
sem-4, was chosen for the further studies. SEM-4 is a zinc-finger transcription factor and is important for development of neuronal, mesodermal and vulval lineages in C.elegans. C. elegans with
sem-4 mutation, or overexpressing
sem-4 are viable and readily available, which makes it possible to test for the importance of dosage effect of SEM-4 in BRAP-2/SKN-1/ROS detoxification pathway. While
brap-2 mutant worms demonstrate higher levels of
gst-4 expression, a significant reduction in
gst-4 mRNA levels is observed in
sem-4;
brap-2 double mutants before and after paraquat stress. Although no physical interaction between SEM-4 and SKN-1 was observed, a luciferase construct containing the promoter of
gst-4 was activated by co-expression of both SEM-4 and SKN-1 in 293T cells. We also found that higher levels of ROS were generated in
sem-4 and
sem4;
brap-2 mutants in comparison to N2 worms, indicating that SEM-4 is required to prevent overproduction of ROS in vivo. Furthermore, the lifespan of
skn-1 overexpressing worms was significantly prolonged by overexpression of
sem-4 and shortened by deletion of
sem-4. Together, these results indicate a newly identified role of SEM-4 in regulating expression of phase II detoxification enzymes and preventing the harmful effects caused by overproduction of ROS. .