Plasmodium falciparum telomerase:: De novo telomere addition to telomeric and nontelomeric sequences and role in chromosome healing
Plasmodium falciparum telomerase:: De novo telomere addition to telomeric and nontelomeric sequences and role in chromosome healing
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DOI：
10.1128/mcb.18.2.919
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发表时间：
1998-02-01
影响因子：
5.3
通讯作者：
Scherf, A
中科院分区：
文献类型：
--
作者：
Bottius, E;Bakhsis, N;Scherf, A
端粒酶是一种特殊的细胞逆转录酶，在大多数真核细胞的增殖过程中补偿染色体的缩短，促进细胞永生化。单细胞原生动物疟疾寄生虫恶性疟原虫完成其线性染色体复制的机制目前尚不清楚。在这项研究中，首次在恶性疟原虫细胞提取物中发现了端粒酶活性。证明了原生质型端粒酶能从头合成DNA寡核苷酸引物3‘端高度可变的端粒重复序列。通过添加下一个正确的碱基来扩展排列的端粒DNA引物。除了延长原有的端粒序列外，恶性疟原虫端粒酶还可以在非端粒3‘端增加端粒重复序列。在体外，GGGTT序列是添加到非端粒3‘端的主要起始DNA序列。寡核苷酸3‘端的Poly(C)显著改变了新端粒酶增加的重复序列的精确度。非端粒延长的效率取决于3‘末端上游富G盒的存在。基于恶性疟原虫天然染色体断裂点的寡核苷酸引物被有效地用作端粒酶底物。这些结果表明，恶性疟原虫端粒酶参与了染色体的维持和断裂染色体上端粒的重新形成。逆转录酶抑制剂如二脱氧GTP在体外有效地抑制恶性疟原虫端粒酶活性。这些数据表明，疟疾端粒酶是开发能够诱导寄生虫细胞衰老的药物的新靶点。
Telomerase, a specialized cellular reverse transcriptase, compensates for chromosome shortening during the proliferation of most eucaryotic cells and contributes to cellular immortalization. The mechanism used by the single-celled protozoan malaria parasite Plasmodium falciparum to complete the replication of its linear chromosomes is currently unknown. In this study, telomerase activity has for the first time been identified in cell extracts of P. falciparum. The de novo synthesis of highly variable telomere repeats to the 3' end of DNA oligonucleotide primers by plasmodial telomerase is demonstrated. Permutated telomeric DNA primers are extended by the addition of the next correct base. In addition to elongating preexisting telomere sequences, P. falciparum telomerase can also add telomere repeats onto nontelomeric 3' ends. The sequence GGGTT was the predominant initial DNA sequence added to the nontelomeric 3' ends in vitro. Poly(C) at the 3' end of the oligonucleotide significantly alters the precision of the new telomerase added repeats. The efficiency of nontelomeric primer elongation was dependent on the presence of a G-rich cassette upstream of the 3' terminus. Oligonucleotide primers based on natural P. falciparum chromosome breakpoints are efficiently used as telomerase substrates. These results imply that P. falciparum telomerase contributes to chromosome maintenance and to de novo telomere formation on broken chromosomes. Reverse transcriptase inhibitors such as dideoxy GTP efficiently inhibit P. falciparum telomerase activity in vitro. These data point to malaria telomerase as a new target for the development of drugs that could induce parasite cell senescence.