Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
Mol Cell. 2010 Jan 29;37(2):196-210. doi: 10.1016/j.molcel.2009.12.034.
After termination, eukaryotic 80S ribosomes remain associated with mRNA, P-site deacylated tRNA, and release factor eRF1 and must be recycled by dissociating these ligands and separating ribosomes into subunits. Although recycling of eukaryotic posttermination complexes (post-TCs) can be mediated by initiation factors eIF3, eIF1, and eIF1A (Pisarev et al., 2007), this energy-free mechanism can function only in a narrow range of low Mg(2+) concentrations. Here, we report that ABCE1, a conserved and essential member of the ATP-binding cassette (ABC) family of proteins, promotes eukaryotic ribosomal recycling over a wide range of Mg(2+) concentrations. ABCE1 dissociates post-TCs into free 60S subunits and mRNA- and tRNA-bound 40S subunits. It can hydrolyze ATP, GTP, UTP, and CTP. NTP hydrolysis by ABCE1 is stimulated by post-TCs and is required for its recycling activity. Importantly, ABCE1 dissociates only post-TCs obtained with eRF1/eRF3 (or eRF1 alone), but not post-TCs obtained with puromycin in eRF1's absence.
终止后，真核 80S 核糖体仍然与 mRNA、P 位去酰化的 tRNA 和释放因子 eRF1 结合在一起，必须通过解离这些配体并将核糖体分离成亚基来循环利用。尽管真核终止后复合物（post-TCs）的循环可以由起始因子 eIF3、eIF1 和 eIF1A 介导（Pisarev 等人，2007 年），但这种无能量的机制只能在低 Mg(2+)浓度的狭窄范围内发挥作用。在这里，我们报告说 ABCE1，一种保守且必需的 ATP 结合盒（ABC）蛋白家族成员，在广泛的 Mg(2+)浓度范围内促进真核核糖体的循环利用。ABCE1 将 post-TCs 解离成游离的 60S 亚基和与 mRNA 和 tRNA 结合的 40S 亚基。它可以水解 ATP、GTP、UTP 和 CTP。ABCE1 对 post-TCs 的 NTP 水解受到刺激，并且是其循环利用活性所必需的。重要的是，ABCE1 仅解离与 eRF1/eRF3（或仅 eRF1）获得的 post-TCs，而不与 eRF1 缺失时用 puromycin 获得的 post-TCs 解离。
