Li Bibo, Espinal Amin, Cross George A M
Laboratory of Molecular Parasitology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Mol Cell Biol. 2005 Jun;25(12):5011-21. doi: 10.1128/MCB.25.12.5011-5021.2005.
Putative TTAGGG repeat-binding factor (TRF) homologues in the genomes of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major were identified. They have significant sequence similarity to higher eukaryotic TRFs in their C-terminal DNA-binding myb domains but only weak similarity in their N-terminal domains. T. brucei TRF (tbTRF) is essential and was shown to bind to duplex TTAGGG repeats. The RNA interference-mediated knockdown of tbTRF arrested bloodstream cells at G(2)/M and procyclic cells partly at S phase. Functionally, tbTRF resembles mammalian TRF2 more than TRF1, as knockdown diminished telomere single-stranded G-overhang signals. This suggests that tbTRF, like vertebrate TRF2, is essential for telomere end protection, and this also supports the hypothesis that TRF rather than Rap1 is the more ancient DNA-binding component of the telomere protein complex. Identification of the first T. brucei telomere DNA-binding protein and characterization of its function provide a new route to explore the roles of telomeres in pathogenesis of this organism. This work also establishes T. brucei as an attractive model for telomere biology.
在布氏锥虫、克氏锥虫和硕大利什曼原虫的基因组中鉴定出了假定的端粒重复序列结合因子（TRF）同源物。它们在C端DNA结合myb结构域与高等真核生物的TRF具有显著的序列相似性，但在N端结构域只有较弱的相似性。布氏锥虫TRF（tbTRF）是必需的，并且已证明其能与双链TTAGGG重复序列结合。RNA干扰介导的tbTRF敲低使血流细胞停滞在G(2)/M期，使前循环细胞部分停滞在S期。在功能上，tbTRF更类似于哺乳动物的TRF2而非TRF1，因为敲低会减少端粒单链G突出端信号。这表明tbTRF与脊椎动物的TRF2一样，对端粒末端保护至关重要，这也支持了TRF而非Rap1是端粒蛋白复合体中更古老的DNA结合成分这一假说。首个布氏锥虫端粒DNA结合蛋白的鉴定及其功能表征为探索端粒在该生物体发病机制中的作用提供了一条新途径。这项工作还确立了布氏锥虫作为端粒生物学有吸引力的模型。
