Antisense transcripts are stretches of non coding mRNA that are complementary to the coding sequence. Genome wide studies have shown that RNA antisense transcripts occur commonly within nature. They are generally believed to increase the coding potential of the genetic code and add an overall layer of complexity to gene regulation. So far, it is known that 40% of the human genome is transcribed in both directions, underlining the potential significance of reverse transcription. 
It has been suggested that complementary regions between sense and antisense transcripts would allow generation of double stranded RNA hybrids, which may play an important role in gene regulation. For example, hypoxia-induced factor 1α mRNA and β-secretase mRNA are transcribed bidirectionally, and it has been shown that the antisense transcript acts as a stabilizer to the sense script.