真核生物终止后核糖体复合物的再循环
Recycling of eukaryotic posttermination ribosomal complexes.
作者信息
Pisarev Andrey V, Hellen Christopher U T, Pestova Tatyana V
机构信息
Department of Microbiology and Immunology, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA.
出版信息
Cell. 2007 Oct 19;131(2):286-99. doi: 10.1016/j.cell.2007.08.041.
After translational termination, mRNA and P site deacylated tRNA remain associated with ribosomes in posttermination complexes (post-TCs), which must therefore be recycled by releasing mRNA and deacylated tRNA and by dissociating ribosomes into subunits. Recycling of bacterial post-TCs requires elongation factor EF-G and a ribosome recycling factor RRF. Eukaryotes do not encode a RRF homolog, and their mechanism of ribosomal recycling is unknown. We investigated eukaryotic recycling using post-TCs assembled on a model mRNA encoding a tetrapeptide followed by a UAA stop codon and report that initiation factors eIF3, eIF1, eIF1A, and eIF3j, a loosely associated subunit of eIF3, can promote recycling of eukaryotic post-TCs. eIF3 is the principal factor that promotes splitting of posttermination ribosomes into 60S subunits and tRNA- and mRNA-bound 40S subunits. Its activity is enhanced by eIFs 3j, 1, and 1A. eIF1 also mediates release of P site tRNA, whereas eIF3j ensures subsequent dissociation of mRNA.
在翻译终止后，mRNA和P位点脱酰基tRNA仍与核糖体结合形成终止后复合物（post-TCs），因此必须通过释放mRNA和脱酰基tRNA以及将核糖体解离成亚基来进行循环利用。细菌post-TCs的循环利用需要延伸因子EF-G和核糖体循环因子RRF。真核生物不编码RRF同源物，其核糖体循环机制尚不清楚。我们使用在编码四肽并随后带有UAA终止密码子的模型mRNA上组装的post-TCs来研究真核生物的循环利用，并报告起始因子eIF3、eIF1、eIF1A以及eIF3的一个松散结合亚基eIF3j能够促进真核生物post-TCs的循环利用。eIF3是促进终止后核糖体分裂成60S亚基以及与tRNA和mRNA结合的40S亚基的主要因子。eIF3j、eIF1和eIF1A可增强其活性。eIF1还介导P位点tRNA的释放，而eIF3j确保随后mRNA的解离。
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