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M. Savino - Structural and superstructural features of human telomeric chromatin
a restriction enzyme assay and of AFM imaging, we
demonstrated that nucleosomes shift from telomeric
DNA to an adjacent sequence in a temperature and
ionic strength dependent manner (Pisano et al.,
2007). On the contrary, most nucleosomes formed on
an average sequence remain in the starting position.
Very recently, we found that TRF1 is able to induce
nucleosome mobility (S. P, M. S, S. C., in preparation).
This remodelling activity is specific for telomeric
nucleosomes since TRF1 has no effect on nucleosomes
formed on other sequences. Our findings
support the hypothesis that inherent nucleosome
mobility depends on DNA sequence, and reveal an
unknown property of TRF1 with relevant implications
in telomere structure and dynamics.
Inhibition of telomerase by targeting human
telomere G-quadruplex structures
The characterization of the structure of telomeric
chromatin represents a relevant research issue, not
only as a matter of basic research but also for the
implications in cancer research. In most tumors reactivation
of telomerase allows to overcome the telomeric
checkpoint and to maintain unlimited proliferative
activity. Since telomerase is inactive in somatic
cells, telomerase represents a specific target for anticancer
strategies.
The relationship between human telomere G-quadruplex
structure and chromatin organization could represent
an important way to regulate oncogene transcription.
It has been recently shown that PQS (putative
quadruplex forming sequences) are present in
most proto-oncogenes regulative sequences. In particular,
we have recently found a PQS about 100 bp
upstream of hTERT, encoding the catalytic subunit
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of telomerase, corresponding to a major DNaseI
hypersensitive site. Targeting this site with polypurinic
oligonucleotides gives rise to the formation of
a triple helix structure (Rossetti et al., 2007).
The stability of this unusual DNA structure was
substantially increased by interacting with water
soluble perylene derivatives, and represents a promising
strategy to inhibit telomerase. We synthesized
several polyamine side-chain perylene derivatives
and showed that they are able to induce G-quadruplex
structures and to inhibit telomerase in a cellfree
assay (Franceschin et al., 2008). Our future aim
is to test these molecules for their ability to inhibit
telomerase in vivo.
Selected Publications
Pisano S, Marchioni E, Galati A, Mechelli R, Savino
M, Cacchione S. Telomeric nucleosomes are intrinsically
mobile. J Mol Biol. 2007, 369:1153-62.
Rossetti L, D’Isa G, Mauriello C, Varra M, De
Santis P, Mayol L, Savino M. A model for triple helix
formation on human telomerase reverse transcriptase
(hTERT) promoter and stabilization by specific
interactions with the water soluble perylene derivative,
DAPER. Biophys Chem. 2007, 129:70-81.
Franceschin M, Lombardo CM, Pascucci E,
D’Ambrosio D, Bianco A, Ortaggi G, Savino M. The
number and distances of positive charges of
polyamine side chains in a series of perylene
diimides significantly influence their ability to induce
G-quadruplex structures and inhibit human telomerase.
Bioorg Med Chem. 2008, 16:2292-304.