Sequence-specific and 3'-end selective single-strand DNA binding by the Oxytricha nova telomere end binding protein alpha subunit.
Biochemistry
; 42(31): 9269-77, 2003 Aug 12.
Article
em En
| MEDLINE
| ID: mdl-12899613
ABSTRACT
Oxytricha nova telomere end binding protein (OnTEBP) specifically recognizes and caps single-strand (T(4)G(4))(2) telomeric DNA at the very 3'-ends of O. nova macronuclear chromosomes. The discovery of proteins homologous to the N-terminal domain of the OnTEBP alpha subunit in Euplotes crassus, Schizosaccharomyces pombe, and Homo sapiens suggests that related proteins are widely distributed in eukaryotes. Previously reported crystal structures of the ssDNA binding domain of the OnTEBP alpha subunit both uncomplexed and complexed with telomeric ssDNA have suggested specific mechanisms for sequence-specific and 3'-end selective recognition of the single-strand telomeric DNA. We now describe comparative binding studies of ssDNA recognition by the N-terminal domain of the OnTEBP alpha subunit. Addition of nucleotides to the 3'-end of the TTTTGGGG telomere repeat decreases the level of alpha binding by up to 7-fold, revealing a modest specificity for a 3'-terminus relative to an internal DNA binding site. Nucleotide substitutions at specific positions within the t(1)t(2)t(3)T(4)G(5)G(6)G(7)G(8) repeat show that base substitutions at some sites do not substantially decrease the binding affinity (<2-fold for lowercase letters), while substitutions at other sites dramatically reduce the binding affinity (>20-fold decrease for the uppercase bold letter). Comparison of the structural and binding data provides unique insights into the ways in which proteins recognize and bind single-stranded DNA.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
DNA de Cadeia Simples
/
Proteínas de Protozoários
/
Telômero
/
Oxytricha
/
Proteínas de Ligação a Telômeros
Limite:
Animals
Idioma:
En
Ano de publicação:
2003
Tipo de documento:
Article