Direct photocleavage of HIV-DNA by quinacridine derivatives triggered by triplex formation.
Amino-p-quinacridine compounds (PQs) have been shown to stabilize strongly and specifically triple-helical DNA. Moreover, these derivatives display photoactive properties that make them efficient DNA cleavage agents. We exploited these two properties (triplex-specific binding and photoactivity) to selectively cleave a double-stranded (ds)DNA sequence present in the HIV-1 genome. Cleavage was first carried out on a linearized plasmid (3300 bp) containing the HIV polypurine tract (PPT) that allowed targeting by a triplex-forming oligonucleotide (TFO). PQ(3)(), the most active compound of the series, efficiently cleaved double-stranded DNA in the vicinity of the PPT when this sequence had formed a triplex with a 16-mer TFO. Investigation of the cleavage at the molecular level was addressed on a short DNA fragment (56 bp); the photoinduced cleavage by PQ(3)() occurred only in the presence of the triple helix. Nevertheless, unusual cleavage patterns were observed: damage was observed at guanines located 6-9 bp away from the end of the triple helical site. This cleavage is very efficient (up to 60%), does not require alkaline treatment, and is observed on both strands. A quinacridine-TFO conjugate produced the same cleavage pattern. This observation, along with others, excludes the hypothesis of a triplex-induced allosteric binding site of PQ(3 )()adjacent to the damaged sequence and indicates that PQ(3 )()preferentially binds in the vicinity of the 5'-triplex junction. Irradiation in the presence of TFO-conjugates with acridine (an intercalative agent) and with the tripeptide lys-tryp-lys led to a complete inhibition of the photocleavage reaction. These results are interpreted in terms of competitive binding and of electron-transfer quenching. Together with the findings of simple mechanistic investigations, they led to the conclusion that the photoinduced damage proceeds through a direct electron transfer between the quinacridine and the guanines. This study addresses the chemical mechanism leading to strand breakage and characterizes the particular photosensitivity of the HIV-DNA target sequence which could be an oxidative hot spot for addressed photoinduced strand scission by photosensitizers.
Teulade-Fichou
M P
MP
Laboratoire de Chimie des Interactions Moléculaires, Collège de France, CNRS UPR 285, 11 place Marcelin Berthelot, 75005 Paris, France.
Perrin
D
D
Boutorine
A
A
Polverari
D
D
Vigneron
J P
JP
Lehn
J M
JM
Sun
J S
JS
Garestier
T
T
Helene
C
C
D000609:Aminoacridines / Q000737:chemistry* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D004249:DNA Damage; D004279:DNA, Viral / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D015497:HIV-1 / Q000235:genetics*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000737:chemistry / Q000378:metabolism; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism
D000609:Aminoacridines; D004279:DNA, Viral; D017319:Photosensitizing Agents; C024829:8-hydroxyguanine; D006147:Guanine