Early dihydrofolate reductase gene amplification events in CHO cells usually occur on the same chromosome arm as the original locus.
Early dihydrofolate reductase gene amplification events in CHO cells usually occur on the same chromosome arm as the original locus.
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CHO细胞中的早期二氢叶酸还原酶基因扩增事件通常发生在与原始基因座相同的染色体臂上。
作者：
B. Trask;J. Hamlin
我们使用荧光原位杂交技术检测CHO细胞早期DNA序列扩增事件的产物。选择9个独立的细胞群体对0.4微米的甲氨蝶呤（MTX）产生抗性，并将有丝分裂的染色体扩散与克隆的混合物杂交，这些克隆体代表了来自二氢叶酸还原酶（DHFR）位点的约273 kb的连续DNA序列。在9个群体中，8个包含扩增了DHFR结构域的细胞。其余群体的细胞仅在2号染色体和Z2号染色体上显示两个单拷贝位点。在8个扩增子中，1个在2号染色体上携带扩增的DHFR基因，6个在Z2号染色体上，1个在未识别的染色体上。一些培养物在其他染色体上携带额外的扩增基因，可能是由于桥/断裂/融合周期或易位。在8个扩增子中的6个中，两个单拷贝亲本基因座都在其原始位置被检测到，并且扩增子簇位于至少50兆碱基（Mb）以外的同一染色体臂上，通常位于末端。扩增仅在一个人群中发生在DHFR基因的原始位点或其附近。我们的结果与模型不一致，在模型中，最初的扩增事件发生在亲本位点的过度复制，然后在loco中重组。由于扩增的DHFR序列最常发生在与亲本DHFR基因相同的染色体臂上，但与亲本DHFR基因距离相当远，因此我们的结果与姐妹染色单体在相隔很远的位点之间交换或与类似于细菌转位的保守染色体内复制形式最相容。
We used fluorescence in situ hybridization to examine the products of early DNA sequence amplification events in CHO cells. Nine independent populations of cells were selected for resistance to 0.4 microM methotrexate (MTX), and mitotic chromosome spreads were hybridized to a mixture of cloned cosmids representing approximately 273 kb of contiguous DNA sequence from the dihydrofolate reductase (DHFR) locus. Of the nine populations, eight contain cells that have amplified the DHFR domain. Cells in the remaining population displayed only the two single-copy loci on chromosomes 2 and Z2. Of the eight amplificants, one carries amplified DHFR genes on chromosome 2, six on chromosome Z2, and one on an unidentified chromosome. Some cultures carry additional amplified genes on other chromosomes, probably resulting from bridge/breakage/fusion cycles or translocations. In six of the eight amplificants, both single-copy parental loci are detected at their original positions, and amplicon clusters are situated at least 50 megabases (Mb) away on the same chromosome arm, often at the termini. Amplification occurred at or close to the original site of the DHFR gene in only one population. Our results are not consistent with models in which initial amplification events occur by over-replication of the parental locus followed by recombination in loco. Because amplified DHFR sequences occur most often on the same chromosome arm as the parental DHFR gene but at a considerable distance from it, our results are most compatible with either sister chromatid exchange between widely separated sites or with a form of conservative intrachromosomal duplication analogous to transposition in bacteria.
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影响因子：
56.9
作者：
BISHOP, JM
通讯作者：
BISHOP, JM
基因扩增、耐药性和癌症。
影响因子：
11.2
作者：
Schimke,RT
通讯作者：
Schimke,RT
新的 DNA 重排与二氢叶酸还原酶基因扩增有关。
DOI：
--
发表时间：
1984
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Federspiel,NA;Beverley,SM;Schilling,JW;Schimke,RT
通讯作者：
Schimke,RT
间期细胞核中 DNA 序列的接近度与基因组距离相关，并允许跨 250 kilobase 对的粘粒进行排序。
影响因子：
4.4
作者：
Trask,B;Pinkel,D;vandenEngh,G
通讯作者：
vandenEngh,G
荧光激活细胞分选显示快速自发二氢叶酸还原酶基因扩增。
DOI：
10.1073/pnas.80.12.3711
发表时间：
1983
影响因子：
11.1
作者：
Johnston,RN;Beverley,SM;Schimke,RT
通讯作者：
Schimke,RT