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溶组织内阿米巴TIF-IA的鉴定:人核糖体RNA转录起始因子-IA在溶组织内阿米巴中的假定同源物。

Identification of EhTIF-IA: The putative E. histolytica orthologue of the human ribosomal RNA transcription initiation factor-IA.

作者信息

Srivastava Ankita, Bhattacharya Alok, Bhattacharya Sudha, Jhingan Gagan Deep

机构信息

School of Environmental Sciences, Jawaharlal Nehru University, New Mehrauli Road, New Delhi 110 067, India.

出版信息

J Biosci. 2016 Mar;41(1):51-62. doi: 10.1007/s12038-016-9587-z.

Abstract

Initiation of rDNA transcription requires the assembly of a specific multi-protein complex at the rDNA promoter containing the RNA Pol I with auxiliary factors. One of these factors is known as Rrn3P in yeast and Transcription Initiation Factor IA (TIF-IA) in mammals. Rrn3p/TIF-IA serves as a bridge between RNA Pol I and the pre-initiation complex at the promoter. It is phosphorylated at multiple sites and is involved in regulation of rDNA transcription in a growth-dependent manner. In the early branching parasitic protist Entamoeba histolytica, the rRNA genes are present exclusively on circular extra chromosomal plasmids. The protein factors involved in regulation of rDNA transcription in E. histolytica are not known. We have identified the E. histolytica equivalent of TIF-1A (EhTIF-IA) by homology search within the database and was further cloned and expressed. Immuno-localization studies showed that EhTIF-IA co-localized partially with fibrillarin in the peripherally localized nucleolus. EhTIF-IA was shown to interact with the RNA Pol I-specific subunit RPA12 both in vivo and in vitro. Mass spectroscopy data identified RNA Pol I-specific subunits and other nucleolar proteins to be the interacting partners of EhTIF-IA. Our study demonstrates for the first time a conserved putative RNA Pol I transcription factor TIF-IA in E. histolytica.

摘要

核糖体DNA(rDNA)转录的起始需要在rDNA启动子处组装一个特定的多蛋白复合物,该复合物包含RNA聚合酶I及辅助因子。其中一个因子在酵母中称为Rrn3P,在哺乳动物中称为转录起始因子IA(TIF-IA)。Rrn3p/TIF-IA作为RNA聚合酶I与启动子处预起始复合物之间的桥梁。它在多个位点被磷酸化,并以生长依赖的方式参与rDNA转录的调控。在早期分支的寄生原生生物溶组织内阿米巴中,rRNA基因仅存在于环状染色体外质粒上。溶组织内阿米巴中参与rDNA转录调控的蛋白质因子尚不清楚。我们通过数据库中的同源性搜索鉴定出了溶组织内阿米巴的TIF-1A等效物(EhTIF-IA),并进一步进行了克隆和表达。免疫定位研究表明,EhTIF-IA与外周定位核仁中的纤维蛋白原部分共定位。EhTIF-IA在体内和体外均显示与RNA聚合酶I特异性亚基RPA12相互作用。质谱数据确定RNA聚合酶I特异性亚基和其他核仁蛋白是EhTIF-IA的相互作用伙伴。我们的研究首次证明了溶组织内阿米巴中存在一种保守的假定RNA聚合酶I转录因子TIF-IA。

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