A genetic polymorphism within the third poly(A) signal of the DHFR gene alters the polyadenylation pattern of DHFR transcripts in CHL cells.
A genetic polymorphism within the third poly(A) signal of the DHFR gene alters the polyadenylation pattern of DHFR transcripts in CHL cells.
复制标题
DHFR 基因的第三个 Poly(A) 信号内的遗传多态性改变了 CHL 细胞中 DHFR 转录物的多腺苷酸化模式。
DOI：
10.1093/nar/22.13.2694
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发表时间：
1994
影响因子：
14.9
通讯作者：
Melera,PW
中科院分区：
文献类型：
--
作者：
Yang,H;Melera,PW
中国仓鼠肺细胞中存在两个多态二氢叶酸还原酶（DHFR）等位基因，分别为20k和21k。每个等位基因转录出三个长度不同的转录本，由于三个poly(a)位点的不同利用，这些转录本的表达在等位基因之间存在显著差异。来自20k等位基因的转录本在第一个聚(A)位点优先聚腺苷化，而来自21k等位基因的转录本在第三个位点优先聚腺苷化。在本研究中，瞬态表达实验证明，包含三个DHFR聚(a)位点的2.1 kb基因组片段足以在COS细胞中瞬时表达的CAT-DHFR转录物上复制等位基因特异性聚腺苷化模式。位点定向诱变允许鉴定负责这种等位基因特异性聚腺苷化的序列元件。这些研究表明，第三个多聚(a)信号序列的单碱基变化，将21 K等位基因的一致AAUAAA信号改变为20 K等位基因的弱AAUAAU信号，是导致两个等位基因聚腺苷化差异显著的主要原因。因此，由于第三个聚(a)信号序列的单碱基变化，位于上游1.2 kb的第一个聚(a)位点的利用发生了巨大变化。
Two polymorphic dihydrofolate reductase (DHFR) alleles, termed 20 K and 21 K, exist in Chinese hamster lung cells. Three major transcripts of different lengths are transcribed from each allele, and the expression of these transcripts differs dramatically between the alleles as a result of differential utilization of three poly(A) sites. Transcripts from the 20 K allele are preferentially polyadenylated at the first poly(A) site, while those from the 21 K allele are preferentially polyadenylated at the third site. In this study, transient expression experiments were used to demonstrate that a 2.1 kb genomic fragment containing the three DHFR poly(A) sites is sufficient to reproduce the allelespecific polyadenylation pattern on transiently expressed CAT-DHFR transcripts in COS cells. Sitedirected mutagenesis allowed identification of the sequence elements which are responsible for this allele-specific polyadenylation. These studies indicate that a single-base change in the third poly(A) signal sequence, which alters the consensus AAUAAA signal in the 21 K allele to a weak AAUAAU signal in the 20 K allele, is primarily responsible for the dramatic difference in polyadenylation between the two alleles. Thus, as a result of this single-base change in the third poly(A) signal sequence, utilization of the first poly(A) site, located 1.2 kb upstream, changes dramatically.