Recent analyses of the human genome and available data about the other higher eukaryotic genomes have revealed that, in contrast to Eubacteria and Archaea, only a small fraction of the genetic material (ca 1.5%) codes for proteins. Most of genomic DNA and its RNA transcripts are involved in regulation of gene expression, which can be exerted at either the transcriptional level, controlling whether a gene is transcribed and to what extent, or at the post-translational level, regulating the fate of the transcribed RNA molecules, including their stability, efficiency of their translation and subcellular localization. Noncoding RNA genes produce functional RNA molecules (ncRNAs) rather than encoding proteins. These stable RNAs act by multiple mechanisms such as RNA-RNA base pairing, RNA-protein interactions and intrinsic RNA activity, as well as regulate diverse cellular functions, including RNA processing, mRNA stability, translation, protein stability and secretion. Non-protein-coding RNAs are known to play significant roles. Along with transfer RNAs, ribosomal RNAs and mRNAs, ncRNAs contribute to gene splicing, nucleotide modification, protein transport and regulation of gene expression.