Synthesis and binding properties of oligonucleotides carrying nuclear localization sequences

The synthesis of oligonucleotides carrying nuclear localization peptide seq uences is described using two strategies: first, oligonucleotides carrying a thiol group at the 5' end were reacted with maleimido peptides; second, p eptide and oligonucleotide were prepared stepwise on the same support, yiel ding oligonucleotide-3'-peptide conjugates. This second approach was thorou ghly studied. Using amino acids and small peptides as model compounds, some side reactions were analyzed, detected, and minimized. Oligonucleotides co mplementary to Ha-ras gene and carrying nuclear localization peptides at th e 3' and 5' ends were prepared. Melting temperature studies showed that dup lexes containing nuclear localization peptides were more stable than duplex es with unmodified oligonucleotides. Moreover, oligonucleotide-peptide conj ugates maintain a good mismatch discrimination when they bind to their targ et RNA.