Target practice: aiming at satellite repeats with DNA minor groove binders

Much progress has been made in recent years in developing small molecules that target the minor groove of DNA. Striking advances have led to the design of synthetic molecules that recognize specific DNA sequences with affinities comparable to those of eukaryotic transcription factors. This makes it feasible to modulate or inhibit DNA/protein interactions in vivo, a major step towards the development of general strategies of anti-gene therapy. Examples from anti-parasitic drugs also suggest that synthetic molecules can affect a variety of cellular functions crucial to cell viability by more generally targeting vast portions of genomes based on their biased base composition. This provides a rationale for developing approaches based on selective interactions with broad genomic targets such as satellite repeats that are associated with structural or architectural components of chromatin essential for cellular proliferation. Using examples drawn from the Drosophila melanogaster model system, we review here the use of synthetic polyamides or diamidines that bind the DNA minor groove and can be used as highly selective agents capable of interfering with specific protein/DNA interactions that occur in A+T-rich repeated sequences that constitute a significant portion of eukaryotic genomes. The satellite localization of cellular proteins that bind the minor groove of DNA via domains such as the AT hook motif is highly sensitive to these molecules. A major consequence of the competition between these proteins and their synthetic mimics is an alteration of the nuclear localization and function of proteins such as topoisomerase II, a major target of anti-cancer drugs.