A misfolded form of the prion protein (PrP) is the primary
culprit
in mammalian prion diseases. It has been shown that nucleic acids
catalyze the misfolding of cellular PrP into a scrapie-like conformer.
It has also been observed that the interaction of PrP with nucleic
acids is nonspecific and that the complex can be toxic to cultured
cells. No direct correlation has yet been drawn between changes in
PrP structure and toxicity due to nucleic acid binding. Here we asked
whether different aggregation, stability, and toxicity effects are
detected when nonrelated DNA sequences interact with recombinant PrP.
Using spectroscopic techniques to analyze PrP tertiary and secondary
structure and cellular assays to assess toxicity, we found that rPrP–DNA
interactions lead to different aggregated species, depending on the
sequence and size of the oligonucleotide tested. A 21-mer DNA sequence
(D67) induced higher levels of aggregation and also dissimilar structural
changes in rPrP, compared to binding to oligonucleotides with the
same length and different nucleotide sequences or different GC contents.
The rPrP–D67 complex induced significant cell dysfunction,
which appears to be correlated with the biophysical properties of
the complex. Although sequence specificity is not apparent for PrP–nucleic
acid interactions, we believe that particular nucleic acid patterns,
possibly related to GC content, oligonucleotide length, and structure,
govern PrP recognition. Understanding the structural and cellular
effects observed for PrP–nucleic acid complexes may shed light
on the still mysterious pathology of the prion protein.