雷公藤是一个有着悠久、广泛应用历史的中药。雷公藤甲素(Triptolide, TPL)是雷公藤的主要活性成分之一。近年来大量体内和体外的研究证明,Triptolide对多种癌症如白血病、乳腺癌、胰腺癌及肺癌等均有良好的抗肿瘤活性。最近的研究发现,TPL除了特异地影响某些蛋白和信号通路以外,还会抑制广泛的基因转录,但其作用机理有待进一步明确。
中科院上海药物研究所俞强课题组对Triptolide抑制广泛基因转录的分子机制进行了深入研究。研究发现,Triptolide通过促进RNA聚合酶II中最大及最主要的功能亚基Rpb1磷酸化,以及随后的Rpb1的泛素化降解,从而抑制基因的转录。Rpb1上游激酶PTEF-b在Triptolide诱导的Rpb1的磷酸化的过程中发挥着正调控作用。研究还发现,Triptolide可以诱导DNA损伤。这些研究提示,Triptolide通过造成细胞的DNA损伤,从而激活P-TEFb,使其磷酸化Rpb1,造成Rpb1的降解,从而抑制了广谱的基因转录。
Triptolide是一个具有多种生物活性的化合物,阐明它的分子作用机制对于其和雷公藤今后在临床上合理的使用具有重要的指导意义。该研究于9月13日在线发表于PLOS ONE上。
研究工作得到了国家自然科学基金委,国家科技部,国家重大科技专项和上海市科委的资助。(生物谷Bioon.com)
doi:10.1371/journal.pone.0024407
PMC:
PMID:
Triptolide (TPL) Inhibits Global Transcription by Inducing Proteasome-Dependent Degradation of RNA Polymerase II (Pol II)
Ying Wang1, Jin-jian Lu1,2, Li He1, Qiang Yu1*
Triptolide (TPL), a key biologically active component of the Chinese medicinal herb Tripterygium wilfordii Hook. f., has potent anti-inflammation and anti-cancer activities. Its anti-proliferative and pro-apoptotic effects have been reported to be related to the inhibition of Nuclear Factor κB (NF-κB) and Nuclear Factor of Activated T-cells (NFAT) mediated transcription and suppression of HSP70 expression. The direct targets and precise mechanisms that are responsible for the gene expression inhibition, however, remain unknown. Here, we report that TPL inhibits global gene transcription by inducing proteasome-dependent degradation of the largest subunit of RNA polymerase II (Rpb1) in cancer cells. In the presence of proteosome inhibitor MG132, TPL treatment causes hyperphosphorylation of Rpb1 by activation of upstream protein kinases such as Positive Transcription Elongation Factor b (P-TEFb) in a time and dose dependent manner. Also, we observe that short time incubation of TPL with cancer cells induces DNA damage. In conclusion, we propose a new mechanism of how TPL works in killing cancer. TPL inhibits global transcription in cancer cells by induction of phosphorylation and subsequent proteasome-dependent degradation of Rpb1 resulting in global gene transcription, which may explain the high potency of TPL in killing cancer.