生物通报道：厦门大学生科院韩家淮教授回国后最富有代表性的成果就是发现了细胞坏死的“开关”，这个“开关”的重要性在于：细胞的“好死”或“坏死”，极大地影响了人类的健康。近期其研究组又进一步获得该领域研究新发现，介绍了这个重要过程中发现的途径新成员：MLKL等方面的新发现，以及先天免疫应答细胞因子调控研究的新成果。

在第一篇文章“A Potential Suppressive Effect of Natural Antisense IL-1β RNA on Lipopolysaccharide-Induced IL-1β Expression”中，研究人员发现先天性免疫应答相关的基因中一些位点能进行反义转录，从而揭示了一种新型的细胞因子表达调控的机制。

尽管半数以上的基因位点都被认为具有反义转录，，但是细胞因子表达过程中是否涉及反义转录还未有定论。在这篇文章中，研究人员发现先天性免疫应答相关的基因中一些位点能进行反义转录，他们分析了一些反义RNA的作用，如anti-4-1BBL, anti-p100, and anti-IL-1β。

结果发现反义IL-1β转录的过度表达能抑制IL-1β的表达，这虽然不会改变IL-1β启动子的甲基化状态，但是染色质免疫沉淀分析显示，anti-IL-1β转录能通过减少启动子H3K4的三甲基化，而改变IL-1β的染色质结构，从而调控了IL-1β的表达。

这一研究结果揭示出一些先天免疫相关基因的反义转录在调控细胞因子表达方法发挥了重要作用。

另外，这一研究组还利用基因敲除新技术- TALEN获得了MLKL 基因敲除小鼠，证实了MLKL在程序性细胞坏死中至关重要的作用。

程序性细胞坏死（necroptosis）是近几年发现的一种重要的细胞程序性死亡方式。2009年，程序性细胞坏死的关键调节蛋白-RIP3的鉴定是细胞坏死领域的一个里程碑。2012年，MLKL被发现是RIP3 下游的另一个调节细胞坏死的关键蛋白，这成为该领域的另一个重大突破。但是MLKL在细胞坏死中的作用并没有直接的体外（in vitro）与体内（in vivo）的遗传学证据。

在这项研究中，研究人员利用基因敲除新技术- TALEN获得了MLKL 基因敲除小鼠，这株小鼠可以正常出生，生长，繁殖，与野生型没有异样，通过分离到的MLKL-/- MEF和巨噬细胞系研究证实MLKL是程序性细胞坏死必不可少的蛋白；在急性胰腺炎组织内存在大量腺泡细胞发生坏死，他们发现MLKL敲除后可以缓解小鼠的胰腺炎炎症，减少坏死的腺泡细胞数量，这表明MLKL 参与了胰腺炎腺泡细胞坏死。此外，作者证实MLKL介导的细胞坏死没有参与炎症相关的感染性休克（septic shock）。

该研究证实了MLKL在程序性细胞坏死中至关重要的作用，同时为治疗急性胰腺炎提供了一个新的药物靶点。

原文摘要：

A Potential Suppressive Effect of Natural Antisense IL-1β RNA on Lipopolysaccharide-Induced IL-1β Expression.

Although more than half of genomic loci are believed to have antisense transcription, whether antisense transcription is involved in cytokine expression has not been studied. In this study, we show that some loci of innate immunity related genes do have antisense transcripts. We investigated the effect of several antisense RNAs, including anti-4-1BBL, anti-p100, and anti-IL-1β, on their cognate sense gene's expression in macrophages. We found that overexpression of antisense IL-1β transcript suppressed IL-1β expression. Anti-IL-1β is complementary to the sequence in the 5' upstream region of the IL-1β promoter. Its mediated inhibition of IL-1β production occurred at the transcriptional level. Anti-IL-1β did not alter the methylation status of the IL-1β promoter. However, chromatin immunoprecipitation assays revealed that the anti-IL-1β transcript can change the chromatin structure of the IL-1β promoter by decreasing H3K4 trimethylation on the promoter, which is at least part of the mechanism underlying the reduced binding of RNA polymerase II to the IL-1β promoter upon anti-IL-1β expression. Our data suggest that some antisense transcripts of innate immunity-related genes play a role by regulating cytokine expression. 

Mlkl knockout mice demonstrate the indispensable role of Mlkl in necroptosis

Mixed lineage kinase domain-like protein (Mlkl) was recently found to interact with receptor interacting protein 3 (Rip3) and to be essential for tumor necrosis factor (TNF)-induced programmed necrosis (necroptosis) in cultured cell lines. We have generated Mlkl-deficient mice by transcription activator-like effector nucleases (TALENs)-mediated gene disruption and found Mlkl to be dispensable for normal mouse development as well as immune cell development. Mlkl-deficient mouse embryonic fibroblasts (MEFs) and macrophages both showed resistance to necrotic but not apoptotic stimuli. Mlkl-deficient MEFs and macrophages were indistinguishable from wild-type cells in their ability to activate NF-κB, ERK, JNK, and p38 in response to TNF and lipopolysaccharides (LPS), respectively. Consistently, Mlkl-deficient macrophages and mice exhibited normal interleukin-1β (IL-1β), IL-6, and TNF production after LPS treatment. Mlkl deficiency protects mice from cerulean-induced acute pancreatitis, a necrosis-related disease, but has no effect on polymicrobial septic shock-induced animal death. Our results provide genetic evidence for the role of Mlkl in necroptosis.