Genome-wide analysis of transcription factor E2F1 mutant proteins reveals that N- and C-terminal protein interaction domains do not participate in targeting E2F1 to the human genome

Previous studies of E2F family members have suggested that protein-protein interactions may be the mechanism by which E2F proteins are recruited to specific genomic regions. We have addressed this hypothesis on a genome-wide scale using ChIP-seq analysis of MCF7 cell lines that express tagged wild type and mutant E2F1 proteins. First, we performed ChIP-seq for tagged WT E2F1. Then, we analyzed E2F1 proteins that lacked the N-terminal SP1 and cyclin A binding domains, the C-terminal transactivation and pocket protein binding domains, and the internal marked box domain. Surprisingly, we found that the ChIP-seq patterns of the mutant proteins were identical to that of WT E2F1. However, mutation of the DNA binding domain abrogated all E2F1 binding to the genome. These results suggested that the interaction between the E2F1 DNA binding domain and a consensus motif may be the primary determinant of E2F1 recruitment. To address this possibility, we analyzed the in vivo binding sites for the in vitro-derived consensus E2F1 motif (TTTSSCGC) and also performed de novo motif analysis. We found that only 12% of the ChIP-seq peaks contained the TTTSSCGC motif. De novo motif analysis indicated that most of the in vivo sites lacked the 5' half of the in vitro-derived consensus, having instead the in vivo consensus of CGCGC. In summary, our findings do not provide support for the model that protein-protein interactions are involved in recruiting E2F1 to the genome, but rather suggest that recognition of a motif found at most human promoters is the critical determinant.     

MTA1 coregulation of transglutaminase 2 expression and function during inflammatory response

Although both metastatic tumor antigen 1 (MTA1), a master chromatin modifier, and transglutaminase 2 (TG2), a multifunctional enzyme, are known to be activated during inflammation, it remains unknown whether these molecules regulate inflammatory response in a coordinated manner. Here we investigated the role of MTA1 in the regulation of TG2 expression in bacterial lipopolysaccharide (LPS)-stimulated mammalian cells. While studying the impact of MTA1 status on global gene expression, we unexpectedly discovered that MTA1 depletion impairs the basal as well as the LPS-induced expression of TG2 in multiple experimental systems. We found that TG2 is a chromatin target of MTA1 and of NF-κB signaling in LPS-stimulated cells. In addition, LPS-mediated stimulation of TG2 expression is accompanied by the enhanced recruitment of MTA1, p65RelA, and RNA polymerase II to the NF-κB consensus sites in the TG2 promoter. Interestingly, both the recruitment of p65 and TG2 expression are effectively blocked by a pharmacological inhibitor of the NF-κB pathway. These findings reveal an obligatory coregulatory role of MTA1 in the regulation of TG2 expression and of the MTA1-TG2 pathway, at least in part, in LPS modulation of the NF-κB signaling in stimulated macrophages.     

核因子E2相关因子2基因在低氧运动下的表达及其对机体抗氧化能力的调节作用

核因子E2相关因子2 (nuclear factor E2 related factor 2,Nrf2)基因可调节多种抗氧化酶活性并间接影响抗疲劳和抗氧化能力,而低氧环境有助于运动能力的提升。为了考察低氧运动对Nrf2基因敲除小鼠的抗疲劳和抗氧化能力的影响,本研究将敲除Nrf2基因的小鼠置于模拟海拔3 000 m和5 000 m (氧浓度约为14.4%和11.1%)的环境中进行4周的低氧训练。研究发现,模拟海拔3 000 m的低氧运动显著提高了小鼠的力竭跑台运动时间,并减弱了骨骼肌损伤。而模拟海拔5 000 m的低氧运动未出现上述效果。低氧运动显著上调了Nrf2 mRNA表达以及HIF-1α、SOD1、SOD2、GR、GSH-PX、NQO-1和HO-1蛋白表达。模拟海拔3 000 m的低氧运动降低了机体ROS和MDA水平,而模拟海拔5 000 m的低氧运动提高了机体ROS和MDA水平。本研究表明敲除Nrf2抑制了小鼠体内抗氧化酶活性,并降低了小鼠的身体机能。而适当的低氧运动则可通过上调Nrf2和HIF-1α的表达来间接提高抗氧化酶活性,改善机体的氧化-还原状态,从而提高抗疲劳和抗氧化能力。然而,氧浓度过低则会产生相反的效果。     

核因子E2相关因子1诸多亚型的产生机制及其在疾病中的作用

核因子E2相关因子1 (nuclear factor-erythroid 2 related factor 1,Nrf1/Nfe2l1)在个体正常生长发育过程中具有维持细胞内稳态和器官完整性的作用。其功能缺失会产生严重的氧化应激和基因组不稳定等,继而导致肝癌、神经退行性疾病等多种疾病。近年研究发现,Nrf1存在多种具有不同程度活化活性甚至相反活性的亚型,这些亚型的分布可能在肿瘤的发生发展过程中具有重要作用。为了更好地了解Nrf1在组织细胞中所发挥的功能,本文简要介绍Nrf1的发现历程,并从选择性剪切加工、内部选择性翻译起始、翻译后剪切加工等方面阐述Nrf1亚型的产生机制,同时详细阐明“跨膜动态加工”、“位点特异性剪切加工”、“泛素依赖性剪切加工”3种翻译后加工模型的差异。最后,介绍Nrf1各亚型的生物学功能及其产生过程出现异常时在疾病中的作用。本文着重对Nrf1各亚型产生机制及其在疾病中的作用进行综述,力求为寻找肿瘤治疗的新策略提供新的方向。