title: Stimulation of human flap endonuclease 1 by human immunodeficiency virus type 1 integrase: possible role for flap endonuclease 1 in 5'-end processing of human immunodeficiency virus type 1 integration intermediates.
abstract: Human immunodeficiency virus type 1 (HIV-1) DNA integration intermediates consist of viral and host DNA segments separated by a 5-nucleotide gap adjacent to a 5'-AC unpaired dinucleotide. These short-flap (pre-repair) integration intermediates are structurally similar to DNA loci undergoing long-patch base excision repair in mammalian cells. The cellular proteins flap endonuclease 1 (FEN-1), proliferating cell nuclear antigen, replication factor C, DNA ligase I and DNA polymerase delta are required for the repair of this type of DNA lesion. The role of FEN-1 in the base excision repair pathway is to cleave 5'-unpaired flaps in forked structures so that DNA ligase can seal the single-stranded breaks that remain following gap repair. The rate of excision by FEN-1 of 5'-flaps from short- and long-flap oligonucleotide substrates that mimic pre- and post-repair HIV-1 integration intermediates, respectively, and the effect of HIV-1 integrase on these reactions were examined in the present study. Cleavage of 5'-flaps by FEN-1 in pre-repair HIV-1 integration intermediates was relatively inefficient and was further decreased 3-fold by HIV-1 integrase. The rate of removal of 5'-flaps by FEN-1 from post-repair HIV-1 integration intermediates containing relatively long (7-nucleotide) unpaired 5'-tails and short (1-nucleotide) gaps was increased 3-fold relative to that seen with pre-repair substrates and was further stimulated 5- to 10-fold by HIV-1 integrase. Overall, post-repair structures were cleaved 18 times more effectively in the presence of HIV-1 integrase than pre-repair structures. The site of cleavage was 1 or 2 nucleotides 3' of the branch point and was unaffected by HIV-1 integrase. Integrase alone had no detectable activity in removing 5'-flaps from either pre- or post-repair substrates.
authors.affiliation: Lady Davis Institute for Medical Research, SMBD-Jewish General Hospital, McGill AIDS Center, Montreal, Canada. emmanuel.faust@mcgill.ca
authors.forename: Emmanuel A
authors.initials: EA
authors.lastname: Faust
authors.forename: Henry
authors.initials: H
authors.lastname: Triller
mesh_terms: D004260:DNA Repair; D004279:DNA, Viral / Q000235:genetics* / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D045585:Flap Endonucleases; D019427:HIV Integrase / Q000302:isolation & purification / Q000378:metabolism*; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000378:metabolism
chemical_list: D004279:DNA, Viral; D009841:Oligonucleotides; D019427:HIV Integrase; D004706:Endodeoxyribonucleases; D045585:Flap Endonucleases; C468317:FEN1 protein, human