滑动序列对游仆虫中识别+1位和+2位编程性核糖体移码具有关键作用

编程性核糖体移码(programmed ribosomal frameshifting,PRF)广泛存在于生命进化谱系的各个分支,是一种翻译水平上的基因表达调控方式。单细胞真核生物游仆虫(Euplotes)中不仅PRF基因比例高,而且移码类型有+1和+2位两种。本研究从基因组水平对八肋游仆虫(E.octocarinatus)中的+2 PRF基因进行了鉴定,比较分析+1及+2 PRF基因中可能的调控元件。为了探讨游仆虫中滑动序列对移码类型的影响,克隆了八肋游仆虫的+1 PRF基因——η微管蛋白基因,将其构建到含绿色荧光蛋白报告基因的游仆虫大核人工染色体中,转染游仆虫细胞,通过检测GFP的表达来确定不同滑动序列突变体对应的移码类型。结果表明,滑动序列的改变能使游仆虫+1 PRF转变为+2 PRF,且这种移码类型的改变与滑动序列第1个密码子编码何种氨基酸无关。本研究揭示了滑动序列对游仆虫中识别+1和+2位的编程性核糖体移码具有关键作用。

Slippery Sequence Is Important for Distinguishing between +1 and +2 Programmed Ribosomal Frameshifting in Euplotes

Programmed ribosomal frameshifting (PRF) regulates gene expression at the translational level in all branches of life. The single-celled eukaryote Euplotes exhibits frequent PRF. Both +1 PRF and +2 PRF were observed in Euplotes. In this study, we performed a genome-wide investigation of +2 PRF genes in Euplotes octocarinatus. The possible regulatory elements involved in distinguishing between +1 PRF and +2 PRF were compared and analyzed. To explore the relation between frameshift type and slippery sequence, the η tubulin gene of E. octocarinatus, a +1 PRF gene, was cloned into Euplotes macronuclear artificial chromosome that containing a GFP reporter gene. After introducing these DNA molecules into Euploes, the frameshift types corresponding to different slippery sequences were determined by detecting the expression of GFP protein. Our results suggested that the frameshift type converted from +1 PRF to +2 PRF along with the change of slippery sequence. Furthermore, there’s no correlation between the frameshift type and the amino acid coded by the first codon of slippery sequence. Our research suggested that the slippery sequence is important for distinguishing between +1 and +2 programmed ribosomal frameshifting in Euplotes.