CHAPTER 6: Noncoding RNA^†

The human genome is composed of roughly 20 000 genes that are transcribed into messenger RNAs and subsequently translated into protein products. These protein-coding genes comprise 1–2% of the sequence space in the human genome. The remaining 98% of the genome was long believed to be devoid of meaningful information and often referred to as ‘junk DNA’. However, the developments and applications of powerful genomic technologies over the past decade have illuminated a wide variety of previously unappreciated regulatory aspects of the noncoding genome. One notable observation facilitated by advances in high-throughput transcriptome profiling is that the vast majority of the human genome is transcribed into RNA. The RNA produced from noncoding regions of the genome is collectively termed noncoding RNA. Noncoding RNAs come in all shapes and sizes and they play diverse roles in the regulation of gene expression. This chapter provides an overview of several different classes of noncoding RNAs including the details of their initial discovery, the mechanisms through which they regulate gene expression and their biogenesis pathways.