2nd INTERNATIONAL CONFERENCE ON BIOINORGANIC CHEMISTRY
3.
4.
5.
6.
DNA appears to be (in decreasing order):
a) A next neighbour N7 atom of a guanine
(resulting in a cisPt(GG) chelate);
b) A 5' neighbour N7 atom of an adenine
(resulting in a cisPt(AG) chelate);
c) Another N7 atom of a nearby guanine
(resulting in either intrastrand, or interstrand chelates cisPt(GNG) or cross-links
cisPt(G) 2 .);
d) A cross-link with functional groups of a
protein, forming a cisPt(G)(Protein) complex.
The distortion of the double helix in case of
chelation to two adjacent guanines in the same
strand, i.e. in case of formation of cisPt(GG),
is relatively small, as deduced from the fact
that the Watson-Crick base pairs remain intact
at ambient temperatures (seen from low field
imino proton NMR spectra).
The kind of distortion in a double stranded
helix for a decanucleotide with a GG-unit in
the central part can best be described as a kink
in the linear helix with an angle of about 40-70
degrees.
The distortion in double-stranded DNA after
binding of cisPt (to a GG-unit) appears to be
similar as deduced from "P NMR measurements on double-stranded oligonucleotides and
on DNA.
The distortion of the double helix in case of
chelation by the unit GTG (binding through
guanines) is different from a GG-chelate and
apparently much more severe.
ACKNOWLEDGEMENTS
The sponsorship of our research from the Netherlands Foundation for Chemical Research (SON) and for Cancer Research
(KWF) is gratefully acknowledged. Johnson & Matthey is
thanked for generous loans of Platinum.
The colleagues and co-workers mentioned as co-authors in the
references are kindly thanked for their valuable contributions.
REFERENCES
[1] A.T.M. MARCELIS, J.
REEDIJK,
Red. Tray.
Chim. Pays-
-Bas, 102, 121 (1983).
[2) J.
J.H.J. DEN HARTOG, A.M.J. FICHTINGERA.T.M. MARCELIS, in M.P. HACKER et al.
(eds.), «Platinum Coordination complexes in Chemotherapy», Nijhoff, Boston, 1984, p. 39.
REEDIJK,
-SCHEPMAN,
Rev. Port. Quím., 27 (1985)
[3] J.H.J.
DIJK,
DEN HARTOG,
C.
ALTONA,
J.H.
VAN
BooM, J.
REE-
FEBS Letters, 176, 393 (1984).
J.H. VAN BOOM, G.A.
C.A.G. HAASNOOT, J. REEDIJK, J. Am.
Chem. Soc., 106, 1528 (1984).
[5] J.H.J. DEN HARTOG, C. ALTONA, J.H. VAN BooM, H. VAN
DEN ELST, J. REEDIJK, lnorg. Chem., submitted for publication.
[6] A.M.J. FICHTINGER-SCHEPMAN, J.L. VAN DER VEER,
P.H.M. LOHMAN, J.H.J. DEN HARTOG, J. REEDIJK, Biochemistry, in press.
[4] J.H.J.
DEN HARTOG, C. ALTONA,
VAN DER MAREL,
MS3.4 — TU
STEPHEN J. LIPPARD
Department of Chemistry
Massachusetts Institute of Technology
Cambridge, Massachusetts 02139
U.S.A.
THE BINDING OF PLATINUM
COMPLEXES TO DNA
The cis stereochemistry of the anticancer drug cis-diamminedichloroplatinum(II), cis-DDP, is essential for its biological activity [1]. The trans isomer
is cytotoxic but has no antitumor effect. Numerous studies in our laboratory [2] and elsewhere
[3] have demonstrated that the major adduct of
cis-DDP with DNA, formed preferentially at low
drug-to-nucleotide (D/N) ratios, is an intrastrand
crosslink between adjacent guanosine residues. In
this complex, the stereochemistry of which has
been systematically probed by molecular mechanics calculations presented elsewhere at this conference [4], the [cis-Pt(NH 3 ) 2 ] 2 + moiety makes two
bonds to the N7 atoms of the guanine bases which
coordinate in a head-to-head arrangement. The
inactive trans-DDP complex cannot, for stereochemical reasons, form this adduct. What then
are the preferred binding sites, if any, of transDDP on DNA and how might knowledge of
these adducts sharpen our understanding of the
87
MINISYMPOSIA: 3. NUCLEIC ACID METAL ION INTERACTIONS
molecular mechanism of action of platinum anticancer drugs?
To address these questions we have used the large
(Klenow) fragment of DNA polymerase I to map
the binding of trans-DDP to M13mp8 viral DNA.
Through this replication mapping approach [5]
we confirmed that (dG) n , n >_ 2, sequences are the
major cis-DDP binding sites on DNA whereas
considerably lower binding specificity is observed
with the trans isomer. The trans-DDP molecules
show a preference for d(GNG) sequences, where
N is any intervening nucleotide. Such an adduct
has previously been proposed to be important for
cis-DDP on the basis of forward mutagenesis
experiments using the lac I system [6]. It is therefore curious that the replication mapping results
reveal trans-DDP to form d(GNG) adducts more
readily than cis-DDP at comparably low D/N
ratios. The stereochemistry of the binding of
trans-DDP to short synthetic oligonucleotides has
been further examined by NMR studies of chromatographically purified adducts, as will be described.
Previously we showed that the regioselectivity of
the binding of cis-DDP to DNA depends critically
upon the nucleotides flanking the d(GpG) target
site [7]. The binding sites can be switched and
modulated by the presence of an external intercalating reagent, such as ethidium, during platination. This interesting stereochemical modulation
of the sequence-dependent local structure of DNA
has now been further elucidated through studies
of the binding of newly synthesized platinum reagents, such as 1 below, in which the intercalator
is chemically linked to cis-[Pt(en)Cl 2 ],
en = ethylenediamine, by a polymethylene chain
[8]. New DNA binding results with this and
related «tethered» platinum complexes will be
discussed.
CCIIn ` WO
REFERENCES
[1] B. ROSENBERG, Cancer Chemother. Rep., 59, 589 (1975).
[2] J.P. CARADONNA, S.J. LIPPARD, in M.P. HACKER, E.B.
DOUPLE, I.H. KRAKOFF (eds.), «Platinum Complexes in
Cancer Chemotherapy», Martinuns Nijhoff, Boston
(1984), p. 14 and refs. cited therein.
[3] a) P.J. STONE, A.D. KELMAN, F.M. SINEX, M.M. BHARGAVA, H.O. HALVORSON, J. Mol. Biol., 104, 793 (1976);
b) J. REEDIJK, J.H.J. DEN HARTOG, A.M.J. FICHTINGER-SCHEPMAN, A.T.M. MARCELLIS, in M.P. HACKER, E.B.
DOUPLE, I.H. KRAKOFF (eds.), «Platinum Complexes in
Cancer Chemotherapy», Martinus Nijhoff, Boston (1984),
p. 38.
[4] J. KOZELKA, G.A. PETSKO, S.J. LIPPARD, G.J. QUIGLEY,
Rev. Port. Quím., 27, ... (1985).
15] A. PINTO, S.J. LIPPARD, Proc. Nat!. Acad. Sci. USA,
in press.
[6] J. BROUWER, P. VAN DE PUTTE, A.M.J. FICHTINGER-SCHEPMAN, J. REEDIJK, Proc. Natl. Acad. Sci. USA, 78,
7010 (1981).
[7] T.D. TuLLlus, S.J. LIPPARD, Proc. Nat!. Acad. Sci. USA,
79, 3489 (1982).
[8] B.E. BOWLER, L.S. HOLLIS, S.J. LIPPARD, J. Am. Chem.
Soc., 106, 6102 (1984).
MS3.5 — TU
G.L. EICHHORN
P. CLARK
Y.A. SHIN
J.J. BUTZOW
J.M. RIFKIND
R.P. PILLAI
P.P. CHUKNYISKI
D. WAYSBORT
Laboratory of Cellular & Molecular Biology, Gerontology Research Center
National Institute on Aging, National Institutes of Health
DHHS, Baltimore, MD 21224
U.S.A.
-
N
NMe 2
THE INFLUENCE OF METAL ION-NUCLEIC
ACID INTERACTIONS ON GENETIC
INFORMATION TRANSFER (G.I.T.)
I
88
One of the major concerns of our laboratory for
many years has been the interaction of metal ions
with nucleic acids, and the impact of these and
Rev. Port. Quím., 27 (1985)