Mammalian telomeres end in a large duplex loop.
Mammalian telomeres contain a duplex array of telomeric repeats bound to the telomeric repeat- binding factors TRF1 and TRF2. Inhibition of TRF2 results in immediate deprotection of chromosome ends, manifested by loss of the telomeric 3' overhang, activation of p53, and end-to-end chromosome fusions. Electron microscopy reported here demonstrated that TRF2 can remodel linear telomeric DNA into large duplex loops (t loops) in vitro. Electron microscopy analysis of psoralen cross-linked telomeric DNA purified from human and mouse cells revealed abundant large t loops with a size distribution consistent with their telomeric origin. Binding of TRF1 and single strand binding protein suggested that t loops are formed by invasion of the 3' telomeric overhang into the duplex telomeric repeat array. T loops may provide a general mechanism for the protection and replication of telomeres.[1]References
- Mammalian telomeres end in a large duplex loop. Griffith, J.D., Comeau, L., Rosenfield, S., Stansel, R.M., Bianchi, A., Moss, H., de Lange, T. Cell (1999) [Pubmed]
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