Disruption of the telomerase catalytic subunit gene from Arabidopsis inactivates telomerase and leads to a slow loss of telomeric DNA
Disruption of the telomerase catalytic subunit gene from Arabidopsis inactivates telomerase and leads to a slow loss of telomeric DNA
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DOI：
10.1073/pnas.96.26.14813
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发表时间：
1999-12-21
影响因子：
11.1
通讯作者：
Shippen, DE
中科院分区：
文献类型：
--
作者：
Fitzgerald, MS;Riha, K;Shippen, DE
端粒酶是维持真核生物染色体端粒的必需酶。在哺乳动物中，正常再生和生殖组织的终生增殖能力以及去分化状态下的持续生长都需要端粒酶。虽然端粒的重要性在60年前首次在植物中阐明，但对端粒和端粒酶在植物生长发育中的作用知之甚少。本文报道了拟南芥端粒酶逆转录酶基因（AtTERT）的克隆和特性分析。AtTERT基因编码一个分子量为131 kDa的高碱性蛋白，具有所有已知的端粒酶蛋白所共有的逆转录酶和端粒酶特异性基序。AtTERT基因在愈伤组织中的表达量是叶片的10-20倍，不含可检测的端粒酶。将转移DNA插入AtTERT基因的纯合植物缺乏端粒酶活性，证实了该基因的身份和功能。由于野生型拟南芥中的端粒很短，所以发现端粒缺失的植物至少能存活两代是出乎意料的。在没有端粒酶的情况下，端粒每一代下降约500个碱基对，比端粒酶缺陷小鼠的下降速度慢10倍。端粒DNA的逐渐丢失可能反映了每轮DNA复制的核苷酸消耗速率降低，或者每代生物体需要较少的细胞分裂。然而，突变体中端粒的逐渐缩短，无论多么缓慢，最终都是致命的。
Telomerase is an essential enzyme that maintains telomeres on eukaryotic chromosomes. In mammals, telomerase is required for the lifelong proliferative capacity of normal regenerative and reproductive tissues and for sustained growth in a dedifferentiated state. Although the importance of telomeres was first elucidated in plants 60 years ago, little is known about the role of telomeres and telomerase in plant growth and development. Here we report the cloning and characterization of the Arabidopsis telomerase reverse transcriptase (TERT) gene, AtTERT, AtTERT is predicted to encode a highly basic protein of 131 kDa that harbors the reverse transcriptase and telomerase-specific motifs common to all known TERT proteins, AtTERT mRNA is 10-20 times more abundant in callus, which has high levels of telomerase activity, versus leaves, which contain no detectable telomerase. Plants homozygous for a transfer DNA insertion into the AtTERT gene lack telomerase activity, confirming the identity and function of this gene. Because telomeres in wild-type Arabidopsis are short, the discovery that telomerase-null plants are viable for at least two generations was unexpected. In the absence of telomerase, telomeres decline by approximately 500 bp per generation, a rate 10 times slower than seen in telomerase-deficient mice. This gradual loss of telomeric DNA may reflect a reduced rate of nucleotide depletion per round of DNA replication, or the requirement for fewer cell divisions per organismal generation. Nevertheless, progressive telomere shortening in the mutants, however slow, ultimately should be lethal.