期刊
EMBO JOURNAL
卷 20, 期 3, 页码 579-588出版社
OXFORD UNIV PRESS
DOI: 10.1093/emboj/20.3.579
关键词
telomere; t-loop; trypanosome
资金
- NCI NIH HHS [CA70343] Funding Source: Medline
- NIAID NIH HHS [F31 AI009893, 1-F31-AI09893, R01 AI021729, AI21729] Funding Source: Medline
- NIA NIH HHS [R01 AG016642] Funding Source: Medline
- NIGMS NIH HHS [GM31819, R37 GM049046, R01 GM031819, R01 GM049046] Funding Source: Medline
Mammalian telomeres form large duplex loops (t-loops) that may sequester chromosome ends by invasion of the 3' TTAGGG overhang into the duplex TTAGGG repeat array. Here we document t-loops in Trypanosoma brucei, a kinetoplastid protozoan with abundant telomeres due to the presence of many minichromosomes. These telomeres contained 10-20 kb duplex TTAGGG repeats and a 3' TTAGGG overhang. Electron microscopy of psoralen/UV crosslinked DNA revealed t-loops in enriched telomeric restriction fragments and at the ends of isolated minichromosomes. In mammals, t-loops are large (up to 25 kb), often comprising most of the telomere, Despite similar telomere lengths, trypanosome t-loops were much smaller (similar to1 kb), indicating that t-loop sizes are regulated. Coating of non-cross-linked minichromosomes with Escherichia coli single-strand binding protein (SSB) often revealed 3' overhangs at both telomeres and several cross-linked minichromosomes had t-loops at both ends. These results suggest that t-loops and their prerequisite 3' tails can be formed on the products of both leading and lagging strand synthesis. We conclude that t-loops are a conserved feature of eukaryotic telomeres.
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