四膜虫中一种类似Dicer的蛋白质在基因组重排、染色体分离和减数分裂前期具有不同功能。
A Dicer-like protein in Tetrahymena has distinct functions in genome rearrangement, chromosome segregation, and meiotic prophase.
作者信息
Mochizuki Kazufumi, Gorovsky Martin A
机构信息
Department of Biology, University of Rochester, Rochester, New York 14627, USA.
出版信息
Genes Dev. 2005 Jan 1;19(1):77-89. doi: 10.1101/gad.1265105. Epub 2004 Dec 14.
Previous studies indicated that genome rearrangement involving DNA sequence elimination that occurs at late stages of conjugation in Tetrahymena is epigenetically controlled by siRNA-like scan (scn) RNAs produced from nongenic, heterogeneous, bidirectional, micronuclear transcripts synthesized at early stages of conjugation. Here, we show that Dcl1p, one of three Tetrahymena Dicer-like enzymes, is required for processing the micronuclear transcripts to scnRNAs. DCL1 is also required for methylation of histone H3 at Lys 9, which, in wild-type cells, specifically occurs on the sequences (IESs) being eliminated. These results argue that Dcl1p processes nongenic micronuclear transcripts to scnRNAs and is required for IES elimination. This is the first evidence linking nongenic micronuclear transcripts, scnRNAs, and genome rearrangement. Dcl1p also is required for proper mitotic and meiotic segregation of micronuclear chromosomes and for normal chromosome alignment in meiotic prophase, suggesting that DCL1 has multiple functions in regulating chromosome dynamics.
先前的研究表明，在四膜虫接合后期发生的涉及DNA序列消除的基因组重排是由在接合早期合成的非基因、异质、双向、微核转录本产生的类似小干扰RNA（scn）的RNA进行表观遗传控制的。在此，我们表明，四膜虫三种类似Dicer的酶之一Dcl1p是将微核转录本加工成scnRNA所必需的。DCL1对于组蛋白H3赖氨酸9位点的甲基化也是必需的，在野生型细胞中，这种甲基化特异性地发生在被消除的序列（内部消除序列，IESs）上。这些结果表明，Dcl1p将非基因微核转录本加工成scnRNA，并且是IES消除所必需的。这是将非基因微核转录本、scnRNA和基因组重排联系起来的首个证据。Dcl1p对于微核染色体的正常有丝分裂和减数分裂分离以及减数分裂前期的正常染色体排列也是必需的，这表明DCL1在调节染色体动态方面具有多种功能。
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