**3.1 Natural antisense transcript-targeted regulation technology using sense oligonucleotides**

If the mRNA-AS transcript interactions are inhibited, it is speculated that an mRNA-AS transcript-protein complex is not formed and that the mRNA becomes unstable [1, 2]. According to this hypothesis, we used single-stranded *sense* oligonucleotides to block the mRNA-AS transcript interactions at a post-transcriptional level. The sense oligonucleotide harbors the same sequence as that of the relevant mRNA.

We first applied the sense oligonucleotide corresponding to the *iNOS* mRNA sequence to decrease the *iNOS* mRNA levels in hepatocytes [19]. In a search of the literature to date, there are not any other reports on applying sense oligonucleotides to knockdown AS transcript(s) and finally mRNA. After refinement of this method and confirmation of its versatility, we established this method as a natural antisense transcript-targeted regulation (NATRE) technology using sense oligonucleotides [14, 18]. The introduction of sense oligonucleotides may regulate the mRNA levels of AS transcript-expressing genes. Similarly, the sense oligonucleotides to other mRNAs reduced the levels of *IFN-A1* and other mRNAs [14, 20]. Therefore, the introduction of sense oligonucleotides may be used as loss-of-function experiments of AS transcripts.

*The Natural Antisense Transcript-Targeted Regulation Technology Using Sense Oligonucleotides… DOI: http://dx.doi.org/10.5772/intechopen.108281*

In the absence of an AS transcript, a sense oligonucleotide cannot hybridize with the relevant mRNA and does not affect mRNA stability. Therefore, the presence of AS transcript and mRNA-AS transcript interactions are essential for the NATRE technology using sense oligonucleotides.

## **3.2 Design of sense oligonucleotides**
