Michel F, Jaeger L, Westhof E, Kuras R, Tihy F, Xu M Q, Shub D A
Centre de Génétique Moléculaire du Centre National de la Recherche Scientifique (CNRS), Laboratoire Associè à l'Université Pierre et Marie Curie, Gif-sur-Yvette, France.
Genes Dev. 1992 Aug;6(8):1373-85. doi: 10.1101/gad.6.8.1373.
Over 1000 nucleotides may separate the ribozyme core of some group I introns from their 3' splice junctions. Using the sunY intron of bacteriophage T4 as a model system, we have investigated the mechanisms by which proximal splicing events are suppressed in vitro, as well as in vivo. Exon ligation as well as cleavage at the 5' splice site are shown to require long-range pairing between one of the peripheral components of the ribozyme core and some of the nucleotides preceding the authentic 3' splice junction. Consistent with our three-dimensional modeling of the entire sunY ribozyme, we propose that this novel interaction is necessary to drive 5' exon-core transcripts into an active conformation. A requirement for additional stabilizing interactions, either RNA-based or mediated by proteins, appears to be a general feature of group I self-splicing. A role for these interactions in mediating putative alternative splicing events is discussed.
1000多个核苷酸可能会将某些I类内含子的核酶核心与它们的3'剪接位点分隔开来。我们以噬菌体T4的sunY内含子作为模型系统，研究了在体外以及体内近端剪接事件受到抑制的机制。结果表明，外显子连接以及在5'剪接位点的切割需要核酶核心的一个外围组分与真实3'剪接位点之前的一些核苷酸之间进行长程配对。与我们对整个sunY核酶的三维建模结果一致，我们提出这种新型相互作用对于驱动5'外显子-核心转录本进入活性构象是必要的。对基于RNA或由蛋白质介导的额外稳定相互作用的需求似乎是I类自我剪接的一个普遍特征。本文还讨论了这些相互作用在介导假定的可变剪接事件中的作用。
