摘要
转录是基因表达调控的重要环节,对转录起始和延长水平已了解甚多,但对转录终止,尤其是真核生物转录终止还知之甚少。已知原核生物转录终止有两种模式:依赖Rho因子和不依赖于Rho因子的内在型转录终止子。近来在真核生物中也提出了两种转录终止模式:依赖poly(A)加工信号和依赖Sen1的转录终止。基因转录时,随着RNA聚合酶C末端结构域(carboxy-terminal domain,CTD)末端磷酸化的变化,可选择不同的转录终止模式。大部分基因在转录时还存在提前终止的现象:如原核生物的色氨酸操纵子;而在真核生物中,依赖Sen1的转录终止模式事实上就是一种衰减模式。最新研究发现,Mpk1可以阻断依赖Sen1的转录而提前终止,这种阻断作用并不依赖Mpk1的激酶活性,而是通过Mpk1与Paf1复合物结合阻断招募Sen1而实现的。由此看出转录终止在基因表达调控中也具有重要意义。
Regulation of gene expression often occurs at the level of transcription.More recently,the transition from initiation to elongation has been better defined.While much less is known about the mechanism of the transcription termination,particularly in eukaryotes.It’s well known that in prokaryotes,there are two pathways： Rho-dependent termination and Rho-independent termination.In eukaryotes,there are also two transcription termination pathways： poly（A）-dependent and Sen1-dependent termination.The selection of the two PolII termination pathways is regulated by the degree of CTD phosphorylation.Large numbers of genes still exist the phenomenon of premature termination（i.e.,attenuation）.In prokaryotes,trp operons perform this function well.In eukaryotes,Sen1dependent termination pathway in fact functions as a mechanism of attenuation.A new study reveals that Mpk1 can block Sen1-mediated premature transcription termination,which is independent of its catalytic activity.This function is mediated by an interaction between Mpk1 and the Paf1 subunit of the Paf1 elongation complex.In conclusion,it’s meaningful for transcription termination in the regulation of gene expression.
出处
《生命的化学》
CAS
CSCD
2012年第6期550-555,共6页
Chemistry of Life
基金
国家"863"计划项目(2013AA090204)资助
