Flap endonucleases

Henricksen, L.A., Tom, S., Liu, Y. and Bambara, R.A. (2000) Inhibition of flap endonuclease 1 by flap secondary structure and relevance to repeat sequence expansion. J. Biol. Chem., 275,16420-16427. 

DNA metabolism Flap endonuclease-1, thymine DNA glycosylase, Werner DNA helicase... 

Enzymes that remove primers - RNase H - hydrolyzes RNA of DNA-RNA hybrids - Flap endonucleases 1 (FEND -recognizes "flap" (Unannealed portion of RNA) near 5 -end of primer and cleaves downstream in DNA region of primer... 

Two enzymes are required for this. RNase HI removes most of the RNA, leaving a single ribonucleotide next to the DNA component. Flap endonuclease-l (FENl) then removes this ribonucleotide and also any mismatched bases in the DNA component. In this way the inability of DNA polymerase a to proofread is overcome. The excised section of DNA is replaced by DNA polymerase 5 as it synthesizes the next Okazaki fragment. 

Dianova, 1. L, Bohr, V. A., and Dianov, G. L. (2001). Interaction of human AP endonuclease 1 with flap endonuclease 1 and proliferating cell nuclear antigen involved in long-patch base excision repair. Biochemistry 40, 12639-12644. 

DNA flap that is removed by FENl flap endonuclease. Polymerases implicated in synthesis during long-patch BER include Pol /3, Pol 6, and Pol e. Which polymerase is actually used for any particular circumstance is the subject of active investigations. 5. cerevisiae lacks Pol /3, such that the m ority of BER in yeast may occur via the long-patch pathway, using Pol e, Pol 6, and Pol a (Wang et al, 1993). For further details on BER, see Beard and Wilson (2000), Caldecott (2003b), Lindahl and Wood (1999), and Chapter 1 of this book. 

Seleno-thymidine was incorporated onto the 5 -end of an oligonucleotide, where, due to its high nucleophilicity, it was used as a method for labelling DNA, exemplified by the use of fluorescein. The C5 -oxidised thymidine lesion (19) was synthesised and incorporated into DNA to study its biochemical properties. It was found that the lesion was excised by DNA polymerase (3 in the presence of flap endonuclease 1. A C5 -boronic acid derivative has been described that will form a crosslink via a 2, 3 -borate ester with a terminal opposing ribonucleotide. ... 

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