MicroRNA引起mRNA降解关键核酸酶CAF1和POP2的生物进化分析

Evolution Analysis of Key Deadenylase in miRNA Mediated mRNA Degradation

MicroRNA(miRNA)参与调控高等真核生物中三分之一以上基因的表达,其中核酸酶CAF1(CCR4-associated factor 1)及其同源基因POP2在miRNA引发的mRNA 3′端多聚腺苷酸(poly(A))的脱腺苷酸化过程中起了关键作用.通过实时定量RT-PCR的方法检测了小鼠各个组织中CAF1和POP2的相对表达情况,发现CAF1和POP2的组织分布特征不同.大多数组织中CAF1的表达水平明显高于POP2,并且组织间差异很大,特别是在大脑、小脑以及睾丸组织中CAF1的表达量很高,而POP2的表达量和变化幅度都较低.蛋白质序列比对发现,CAF1和POP2是一类进化过程中高度保守的核酸外切酶,在酵母、线虫、果蝇和尾索动物代表物种海鞘中都只存在单一基因,而进化到鱼类后产生了两个同源基因——CAF1和POP2,其中CAF1的氨基酸序列保守性较POP2更高,更加接近于原始的单一序列.CAF1和POP2这一对同源基因氨基酸序列的主要差别在蛋白质的C端.鱼类中POP2的C端序列同CAF1的序列较为接近,而在爬行动物之后POP2产生了与CAF1具有明显差异的C端序列,并逐渐趋于稳定.我们的分析结果同已有的功能研究一致,表明可能在miRNA产生后的进化过程中产生了CAF1和POP2两个同源基因,其中CAF1主要担负miRNA调控mRNA脱腺苷酸化的功能,而POP2可能主要参与其它不同的调控作用。

MicroRNAs（miRNAs） regulate the expression of more than 30% genes in animals.CAF1 and POP2 are exoribonucleases that play a key role in miRNA mediated mRNA deadenylation.The expression of CAF1 and POP2 in different tissues of mouse by qRT-PCR is analyzed.The expression of CAF1 is much higher than POP2 in most tissues,with highest expression level in cerebra,cerebel and testis.Through the alignment of protein sequence,it is found that CAF1 and POP2 are highly conserved exonuclease from yeast to human.Yeast encodes only one CAF1/POP2 homologeous.After the emergence of miRNAs,organism evolved two paralogs-CAF1 and POP2.POP2 are less conserved than CAF1 and contain a distinct amino acid sequences at the C-terminus.The results indicate that CAF1 may mainly take part in mRNA deadenylation mediated by miRNA while POP2 may have other regulatory functions.