Meise Ruth, Tomicic Maja T, Kaina Bernd, Christmann Markus
Department of Toxicology, University Medical Center Mainz, Mainz, Germany.
Biochim Biophys Acta. 2012 Jul;1823(7):1199-207. doi: 10.1016/j.bbamcr.2012.05.008. Epub 2012 May 15.
FRA1 belongs, together with c-Fos and FosB, to the family of Fos proteins that form with members of the ATF and Jun family the transcription factor AP-1 (activator protein 1). Previously we showed that c-Fos protects mouse embryonic fibroblasts against the cytotoxic effects of ultraviolet (UV) light by induction of the endonuclease XPF, leading to enhanced nucleotide excision repair (NER) activity. Here, we analyzed the regulation of FRA1 in glioma cells treated with the anticancer drug nimustine (ACNU) and its role in ACNU-induced toxicity. We show that FRA1 is upregulated in glioblastoma cells following ACNU on mRNA and protein levels. Knockdown of FRA1 by either siRNA or shRNA clearly sensitized glioma cells towards ACNU-induced cell death. Despite decreased AP-1 binding activity upon FRA1 knockdown, this effect is independent on regulation of the AP-1 target genes fasL, ercc1 and xpf. In addition, FRA1 knockdown does not affect DNA repair capacity. However, lack of FRA1 attenuated the ACNU-induced phosphorylation of CHK1 and led to a reduced arrest of cells in G2/M and, thereby, presumably leads to enhanced cell death in the subsequent cell cycle.
FRA1与c-Fos和FosB同属于Fos蛋白家族，该家族与ATF和Jun家族成员共同构成转录因子AP-1（激活蛋白1）。此前我们发现，c-Fos通过诱导核酸内切酶XPF保护小鼠胚胎成纤维细胞免受紫外线（UV）的细胞毒性作用，从而增强核苷酸切除修复（NER）活性。在此，我们分析了抗癌药物尼莫司汀（ACNU）处理的胶质瘤细胞中FRA1的调控及其在ACNU诱导的毒性中的作用。我们发现，在mRNA和蛋白质水平上，胶质母细胞瘤细胞经ACNU处理后FRA1上调。通过siRNA或shRNA敲低FRA1可明显使胶质瘤细胞对ACNU诱导的细胞死亡敏感。尽管敲低FRA1后AP-1结合活性降低，但这种效应独立于AP-1靶基因fasL、ercc1和xpf的调控。此外，敲低FRA1不影响DNA修复能力。然而，缺乏FRA1会减弱ACNU诱导的CHK1磷酸化，并导致细胞在G2/M期的阻滞减少，从而可能导致后续细胞周期中细胞死亡增加。
