In the recent years, novel regulatory functions of non-coding RNAs have been discovered. Non-coding RNAs (ncRNAs) are diverse classes of RNA molecules not translated into proteins that possess intricate regulatory and structural functions. The human genome sequencing performed by the International Human Genome Sequencing Consortium revealed that only 20–25,000 genes are protein coding, corresponding to less than 2% of the human genome (2004). Although the common belief that the remaining and larger portion of the human genome was not functional and considered as “junk DNA”, recent studies based on tiling arrays and RNA deep sequencing show thousands of RNA transcripts not derived from known genes and not encoding proteins (KAPRANOV et al. 2007 ; CARNINCI et al. 2005). These molecules......