S. Rousset et al., 6,4,4'-TRIMETHYLANGELICIN PHOTOADDUCT IMMUNODETECTION IN DNA - INDUCTION AND REPAIR IN FANCONIS-ANEMIA AND NORMAL HUMAN FIBROBLASTS, Journal of photochemistry and photobiology.B, Biology, 38(2-3), 1997, pp. 220-227
6,4,4'-Trimethylangelicin (TMA)-photoinduced monoadducts (MAs) were de
tected and quantified on DNA of normal human and Fanconi's anemia (FA)
fibroblasts (complementation groups A and D) by immuno-electron micro
scopy. TMA-modified DNA was extracted from the cells just after photor
eaction, or after a subsequent 24 h repair period, for analysis of the
MA processing capabilities of the different cell lines. Unmodified DN
A was extracted from the control cells in parallel. The immunoreaction
with antibody 7E3 was performed on single-stranded DNA fragments obta
ined by heat-formamide denaturation. On single-stranded DNA fragments
scanned in the electron microscope, IgC-labeled MA sites appeared as i
solated or clustered IgG molecules, which were not homogeneously distr
ibuted. The isolated IgG and the different clusters (doublets, triplet
s or near-neighbors (within a distance of 250 nucleotides)) were measu
red separately for induction frequency and removal. Few interstrand cr
oss-links (CLs) were present on X-shape DNA fragments. At time zero, t
he distribution patterns of TMA-photoinduced IgG-labeled MA sites and
CLs, and their amount per 10(6) nucleotides, were similar in the three
cell lines. After the 24 h repair period, FA cells from two different
genetic complementation groups demonstrated impaired incisian-excisio
n repair capabilities for both MAs (singlets or clusters) and CLs when
compared with normal cells. In each cell line, the relative proportio
ns of TMA-induced lesions remaining at time 24 h were similar to those
initially induced. This implies analogous processing kinetics towards
the TMA-phatoinduced clusters of MAs and CLs in a given cell line. (C
) 1997 Elsevier Science S.A.