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A sequence-dependent exonuclease activity from Tetrahymena thermophila

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Author(s): Tom Hui-I | Greider Carol

Journal: BMC Biochemistry
ISSN 1471-2091

Volume: 11;
Issue: 1;
Start page: 45;
Date: 2010;
Original page

ABSTRACT
Abstract Background Telomere function requires a highly conserved G rich 3'- overhang. This structure is formed by 5'-resection of the C-rich telomere strand. However, while many nucleases have been suggested to play a role in processing, it is not yet clear which nucleases carry out this 5'-resection. Results We used biochemical purification to identify a sequence-dependent exonuclease activity in Tetrahymena thermophila cell extracts. The nuclease activity showed specificity for 5'-ends containing AA or AC sequences, unlike Exo1, which showed sequence-independent cleavage. The Tetrahymena nuclease was active on both phosphorylated and unphosphorylated substrates whereas Exo1 requires a 5'-phosphate for cleavage. Conclusions The specificities of the enzyme indicate that this novel Tetrahymena exonuclease is distinct from Exo1 and has properties required for 3'-overhang formations at telomeres.
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Tango Rapperswil
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