Deletion of the Tetrahymena thermophila rDNA replication fork barrier region disrupts macronuclear rDNA excision and creates a fragile site in the micronuclear genome.
Deletion of the Tetrahymena thermophila rDNA replication fork barrier region disrupts macronuclear rDNA excision and creates a fragile site in the micronuclear genome.
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四心hymena hythyphila rDNA复制叉屏障区域的缺失破坏了大核RDNA切除，并在微核基因组中产生脆弱的位点。
DOI：
10.1093/nar/gkj466
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发表时间：
2006
影响因子：
14.9
通讯作者：
Kapler GM
中科院分区：
文献类型：
--
作者：
Yakisich JS;Kapler GM
在大核发育过程中，嗜热四膜虫核糖体RNA基因通过染色体断裂序列（Cb s）元件处的位点特异性切割从微核1号染色体上切除，重排成“回文”21 kb微型染色体并广泛扩增。基因扩增起始于5′非转录间隔区的起点，并在发育调节的复制叉屏障（RFB）处向回文结构中心移动。RFB在营养细胞分裂过程中是不活跃的，表明在大核rDNA的形成或扩增中起作用。使用微核（生殖系）转化，我们表明，RFB区域有利于Cbs介导的切除。RFB的缺失抑制了发育中的大核亚群中的染色体断裂，并通过不依赖于CBS的机制促进替代加工。值得注意的是，RFB区域防止二倍体微核中1号染色体的自发断裂。ΔRFB和野生型rDNA杂合的菌株在营养繁殖过程中丢失ΔRFB等位基因和1号染色体的远端左臂。野生型染色体随后在rDNA位点附近片段化，并且两个同源物逐渐被侵蚀，这表明断裂的微核染色体不能被端粒酶“治愈”。这363 bp的片段的删除有效地创建了一个脆弱的网站在微核基因组，提供了第一个证据的非端粒顺式作用的决定因素，其功能是保持结构完整性的有丝分裂真核细胞染色体。
During macronuclear development the Tetrahymena thermophila ribosomal RNA gene is excised from micronuclear chromosome 1 by site-specific cleavage at chromosome breakage sequence (Cbs) elements, rearranged into a ‘palindromic’ 21 kb minichromosome and extensively amplified. Gene amplification initiates from origins in the 5′ non-transcribed spacer, and forks moving toward the center of the palindrome arrest at a developmentally regulated replication fork barrier (RFB). The RFB is inactive during vegetative cell divisions, suggesting a role in the formation or amplification of macronuclear rDNA. Using micronuclear (germline) transformation, we show that the RFB region facilitates Cbs-mediated excision. Deletion of the RFB inhibits chromosome breakage in a sub-population of developing macronuclei and promotes alternative processing by a Cbs-independent mechanism. Remarkably, the RFB region prevents spontaneous breakage of chromosome 1 in the diploid micronucleus. Strains heterozygous for ΔRFB and wild-type rDNA lose the ΔRFB allele and distal left arm of chromosome 1 during vegetative propagation. The wild-type chromosome is subsequently fragmented near the rDNA locus, and both homologs are progressively eroded, suggesting that broken micronuclear chromosomes are not ‘healed’ by telomerase. Deletion of this 363 bp segment effectively creates a fragile site in the micronuclear genome, providing the first evidence for a non-telomere cis-acting determinant that functions to maintain the structural integrity of a mitotic eukaryotic chromosome.
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影响因子：
3.3
作者：
Morrison, TL;Yakisich, JS;Kapler, GM
通讯作者：
Kapler, GM
影响因子：
64.5
作者：
Lambert, S;Watson, A;Carr, AM
通讯作者：
Carr, AM
影响因子：
5.3
作者：
BRUNK, CF;CONOVER, RK
通讯作者：
CONOVER, RK
影响因子：
56.9
作者：
Kirk, KE;Harmon, BP;Blackburn, EH
通讯作者：
Blackburn, EH
影响因子：
3.2
作者：
Mpoke, SS;Wolfe, J
通讯作者：
Wolfe, J