Antisense oligonucleotides and PNAs for sequence-specific regulation of gene expression

It has become increasingly clear in recent years that there are many possible regulatory steps in the pathway from gene to protein: chromatin conformation and transcriptional control; post-transcriptional regulation, particularly splicing, mRNA stability, nuclear cytoplasm transport of mRNAs, natural antisense transcripts; translational and post-translational control. Using antisense strategies it is possible to interfere with most of the regulatory mechanisms underlying gene expression both in embryonic and somatic cells. The specific gene inactivation in a particular cellular context is the necessary step to evaluate its possible biological function. Several different technical approaches based on different methodologies underlie antisense strategies. Among these, antisense oligonucleotides and peptide nucleic acids (PNAs) are considered in this short review. In these experimental approaches it is essential to identify the target genes and the most suitable cellular system. In fact, gene inactivation in somatic cells allows us to study basic questions in cell biology, such as cell cycle regulation, differentiation apoptosis, cell activation, cellular transformation, without having to struggle with the complexities of animal models. We have studied the biological consequences of c-myb, c-fes and Bax genes inactivation in normal and leukemic myeloid cells and their possible therapeutic applications. New delivery systems, based on translocating peptides to efficiently penetrate the cells with antisense oligonucleotides, PNAs and biologically active peptides are also discussed.