| Members of the MAF (proto-) oncogene and CNC families of basic leucine zipper transcription factors (bZIP) play important roles in development, differentiation, mammalian gene expression and stress signalling. We analyzed the regulation of the human small MAF transcription factor family members, MAFF, MAFG and MAFK, as well as two CNC family members, NRF2 and NRF3, in human reproductive tissue. We found that MAFF expression was induced by the proinflammatory cytokines interleukin 1 beta (IL1B) and tumor necrosis factor (TNF) in PHM1-31 myometrial cells. It was particularly interesting that the proinflammatory cytokine Interleukin 6 not affect the expression of MAFF. Additionally, the transcript and protein levels of the highly homologous MAFG and MAFK genes were not modulated by these cytokines. Using electromobility shift assays (EMSA)s we showed that MAFF is capable of heterodimerzing with NRF3, and since they are both highly expressed in the placenta we investigated their role in more detail in this tissue. We found that MAFF and NRF3 are expressed in the anchoring villi from 12 weeks to term. Furthermore, we demonstrated that MAFF and NRF3 are highly expressed in primary placental cytotrophoblasts, but not in placental fibroblasts. This led us to examine whether NRF3 is also regulated by proinflammatory cytokines and we showed that NRF3, is also modulated by TNF in the human JAR placental cell line.;Parallel studies investigated the role NRF2 plays in the antioxidant response of placental cells due to exposure to arsenic. We provided evidence for the involvement of NRF2 by confirming the increase in binding of endogenous NRF2/small MAF heterodimers to Stress Response Element (StRE), and the upregulation of heme oxygenase-1 (HOI) expression, upon exposure of JAR cells to arsenic. Our results suggest a role for MAFF, NRF3 and NRF2 in proinflammatory cytokine control of myometrial and placental gene expression as well as arsenic mediated stress in placental cells. |
