Schuler M A
Department of Cell and Developmental Biology, University of Illinois, Urbana, IL 61801, USA.
Curr Top Microbiol Immunol. 2008;326:39-59. doi: 10.1007/978-3-540-76776-3_3.
Intron sequences in nuclear pre-mRNAs are excised with either the major U2 snRNA-dependent spliceosomal pathway or the minor U12 snRNA-dependent spliceosomal pathway that exist in most eukaryotic organisms. While the predominant dinucleotides bordering each of these types of introns and the catalytic mechanism used in their excision are conserved in plants and animals, several features aiding in the recognition of plant introns are distinct from those in animals and yeast. Along with their short length, high AU content and high variation in their 5' and 3' splice sites and branchpoint consensus sequences are the most prominent characteristics of plant introns. Detailed surveys of site-directed mutant introns tested in vivo and chemically induced and naturally mutant introns analyzed in planta emphasize the effects of changing individual nucleotides in these splice site consensus sequences and highlight a number of noncanonical dinucleotides that are functional in plant systems.
核前体mRNA中的内含子序列可通过大多数真核生物中存在的主要的依赖于U2 snRNA的剪接体途径或次要的依赖于U12 snRNA的剪接体途径切除。虽然与这两类内含子相邻的主要二核苷酸及其切除所使用的催化机制在植物和动物中是保守的，但有助于识别植物内含子的几个特征与动物和酵母中的不同。除了长度短、AU含量高以及5'和3'剪接位点和分支点共有序列高度可变外，植物内含子最突出的特征就是这些。对体内测试的定点突变内含子以及植物中化学诱导和天然突变内含子的详细调查强调了改变这些剪接位点共有序列中单个核苷酸的影响，并突出了一些在植物系统中起作用的非经典二核苷酸。
