Hoffman D C, Prescott D M
Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder 80309-0347, USA.
Nucleic Acids Res. 1996 Sep 1;24(17):3337-40. doi: 10.1093/nar/24.17.3337.
We report the structure of the micronuclear (germline) gene encoding the large catalytic subunit of DNA polymerase alpha (DNA pol alpha) in the ciliate Oxytricha nova. It contains 44 internal eliminated segments (IESs) that divide the gene into 45 macronuclear-destined segments (MDSs) that are in a non-randomly scrambled order with an inversion near the gene center. Odd numbered MDSs 29-43, containing 230 bp out of a total of 4938 bp of macronuclear sequence, are missing from the 14 kb cloned gene. The missing MDSs have not been located but are at least several kilobases from the main body of the gene. The remarkably scrambled DNA pol alpha gene must be extensively cut, re-ordered and spliced and an inversion must occur to produce an unscrambled, functional version of the gene during development of a new macronucleus. Unscrambling is hypothesized to occur by a homologous recombination mechanism guided by repeat sequences at MDS ends.
我们报道了纤毛虫新奥克特里查中编码DNA聚合酶α(DNA polα)大催化亚基的微核(种系)基因的结构。它包含44个内部消除片段(IESs),这些片段将基因分成45个注定进入大核的片段(MDSs),它们以非随机的混乱顺序排列,在基因中心附近有一个倒位。在14kb的克隆基因中,缺少奇数编号的MDSs 29 - 43,在总共4938bp的大核序列中,这些片段包含230bp。缺失的MDSs尚未定位,但至少距离基因主体几千碱基对。这个极度混乱的DNA polα基因必须被广泛切割、重新排序和拼接,并且必须发生一次倒位,才能在新大核发育过程中产生一个解乱的、有功能的基因版本。据推测,解乱过程是通过MDS末端重复序列引导的同源重组机制发生的。