The biological functions of DNA damage recognition proteins are not we
ll understood. Using the band shift assay, we detected in nuclear extr
acts from human carcinoma cell lines damage recognition protein which
bound selectively to W-damaged double-stranded DNA. No consistent corr
elation was found between steady-state levels of the UV-damage recogni
tion protein and either cisplatin cytotoxicity or DNA repair activity;
However, cisplatin treatment caused accumulation of the UV-damage rec
ognition protein. The cisplatin-responsive induction of UV-damage reco
gnition protein in the nucleus was higher in cisplatin-resistant cell
lines than in their parental counterparts. These results imply that th
e level of inducibility in response to treatment, but not the constitu
tive binding activity, of UV-damage recognition protein correlates wit
h cisplatin resistance. Inhibition of UV-damage recognition protein ex
pression by actinomycin and cycloheximide suggests that induction of U
V-damage recognition protein requires de novo RNA and protein synthesi
s, rather than post-translational modification of pre-existing protein
. The increased level of UV-damage recognition protein after cisplatin
treatment could be a direct response to adduct formation, since it co
rrelated with the number of Pt-DNA adducts. However, it could also be
a secondary effect of DNA replication inhibition following DNA damage,
since inhibition of DNA synthesis by aphidicolin and hydroxyurea caus
ed the same induction of UV-damage recognition protein. Inducibility o
f UV-damage recognition protein binding activity by Pt drug treatment
suggests involvement of this protein in drug resistance, although a di
rect link between its function and DNA repair or damage tolerance has
not been demonstrated.