Platinated DNA Affects
Zinc Finger Conformation. Interaction
of a Platinated Single-Stranded Oligonucleotide and the C-Terminal
Zinc Finger of Nucleocapsid Protein HIVNCp7
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Abstract
This paper describes for the first time the intimate
molecular
details of the association between a platinated oligonucleotide and
a zinc finger peptide. Site-specific platination of the guanine in
a single-stranded hexanucleotide gave {[Pt(dien)d(5′-TACGCC-3′)],
Pt(dien)(6-mer)} (<b>II</b>) characterized by mass spectrometry
and <sup>1</sup>H nuclear magnetic resonance (NMR) spectroscopy. The
work extends the study of platinum–nucleobase complex–zinc
finger interactions using small molecules such as [Pt(dien)(9-EtGua)]<sup>2+</sup> (<b>I</b>). The structure of the (34–52) C-terminal
finger of HIV nucleocapsid protein HIVNCp7 (<b>ZF1</b>) was
characterized by <sup>1</sup>H NMR spectroscopy and compared with
that of the N-terminal single finger and the two-finger “intact”
NCp7. Interaction of <b>II</b> with <b>ZF1</b> results
in significant changes in comparison to the “free” uncomplexed
hexanucleotide; the major changes occurring for Trp37 resonances that
are broadened and moved upfield, and other major shifts are for Gln45
(Hε21, Hγ3, Qβ), Met46 (NH, Hγ2), Lys47 (NH,
Qγ), and Glu50 (Hγ2, Hγ3). The Zn–Cys/His
chemical shifts show only marginal deviations. The solution structures
of <b>ZF1</b> and the 6-mer–<b>ZF1</b> and <b>II–ZF1</b> adducts were calculated from the nuclear Overhauser
effect spectroscopy-derived distance constraints. The DNA position
in the <b>II–ZF1</b> adduct is completely different than
in the absence of platinum. Major differences are the appearance of
new Met46–Cyt6 H5 and Trp37–Cyt5 H5 contacts but severe
weakening of the Trp37–Gua4 contact, attributed to the steric
effects caused by Gua4 platination, accompanied by a change in the
position of the aromatic ring. The results demonstrate the feasibility
of targeting specific ZF motifs with DNA-tethered coordination compounds,
such as Pt compounds and Co macrocycles, with implications for drug
targetting and indeed the intimate mechanisms of DNA repair of platinated
DNA