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BMC Biochem. 2010 Nov 16;11:45. doi: 10.1186/1471-2091-11-45.

A sequence-dependent exonuclease activity from Tetrahymena thermophila.

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1
Department of Molecular Biology and Genetics, The Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA.

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.

PMID:
21080963
PMCID:
PMC2998447
DOI:
10.1186/1471-2091-11-45
[Indexed for MEDLINE]
Free PMC Article
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