T4 DNA polymerase (3'-5') exonuclease, an enzyme for the detection and quantitation of stable DNA lesions: the ultraviolet light example.
AUTOR(ES)
Doetsch, P W
RESUMO
Ultraviolet light irradiation of DNA results in the formation of two major types of photoproducts, cyclobutane dimers and 6-4' [pyrimidin-2'-one] -pyrimidine photoproducts. The enzyme T4 DNA polymerase possesses a 3' to 5' exonuclease activity and hydrolyzes both single and double stranded DNA in the absence of deoxynucleotide triphosphate substrates. Here we describe the use of T4 DNA polymerase associated exonuclease for the detection and quantitation of UV light-induced damage on both single and double stranded DNA. Hydrolysis of UV-irradiated single or double stranded DNA by the DNA polymerase associated exonuclease is quantitatively blocked by both cyclobutane dimers and (6-4) photoproducts. The enzyme terminates digestion of UV-irradiated DNA at the 3' pyrimidine of both cyclobutane dimers and (6-4) photoproducts. For a given photoproduct site, the induction of cyclobutane dimers was the same for both single and double stranded DNA. A similar relationship was also found for the induction of (6-4) photoproducts. These results suggest that the T4 DNA polymerase proofreading activity alone cannot remove these UV photoproducts present on DNA templates, but instead must function together with enzymes such as the T4 pyrimidine dimer-specific endonuclease in the repair of DNA photoproducts. The T4 DNA polymerase associated exonuclease should be useful for the analysis of a wide variety of bulky, stable DNA adducts.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=341235Documentos Relacionados
- Construction and characterization of a bacteriophage T4 DNA polymerase deficient in 3'-->5' exonuclease activity.
- The effect of the 3',5' thiophosphoryl linkage on the exonuclease activities of T4 polymerase and the Klenow fragment.
- CCR4, a 3′–5′ poly(A) RNA and ssDNA exonuclease, is the catalytic component of the cytoplasmic deadenylase
- Specificity and efficiency of editing of mismatches involved in the formation of base-substitution mutations by the 3'----5' exonuclease activity of phage T4 DNA polymerase.
- C4-methyldeoxythymidine replacing deoxythymidine in poly[d(A-T)] renders the polymer resistant to the 3'----5' exonuclease activity of the Klenow and T4 DNA polymerases.