Dietrich R C, Incorvaia R, Padgett R A
Department of Molecular Biology, Lerner Research Institute, Cleveland Clinic Foundation, Ohio 44195, USA.
Mol Cell. 1997 Dec;1(1):151-60. doi: 10.1016/s1097-2765(00)80016-7.
Two types of eukaryotic nuclear introns are known: the common U2-dependent class with /GU and AG/ terminal intron dinucleotides, and the rare U12-dependent class with /AU and AC/ termini. Here we show that the U12-dependent splicing system can splice introns with /GU and AG/ termini and that such introns occur naturally. Further, U2-dependent introns with /AU and AC/termini also occur naturally and are evolutionarily conserved. Thus, the sequence of the terminal dinucleotides does not determine which spliceosomal system removes an intron. Rather, the four classes of introns described here can be sorted into two mechanistic classes (U2- or U12-dependent) by inspection of the complete set of conserved splice site sequences.
常见的依赖U2的类型，其内含子末端二核苷酸为/GU和AG/；以及罕见的依赖U12的类型，其末端为/AU和AC/。在此我们表明，依赖U12的剪接系统能够剪接末端为/GU和AG/的内含子，并且此类内含子是自然存在的。此外，末端为/AU和AC/的依赖U2的内含子同样自然存在且在进化上保守。因此，末端二核苷酸的序列并不能决定哪个剪接体系统去除一个内含子。相反，通过检查完整的保守剪接位点序列集，这里描述的四类内含子可分为两个机制类别（依赖U2或依赖U12）。
