Copyright © 2014 John Wiley & Sons, Ltd.
Analyses of the international human genome sequencing results in 2004 converged to a consensual number of ~20,000 protein-coding genes, spanning over <2% of the total genomic sequence. Therefore, the developmental and physiological complexity of human beings remains unaccounted if viewed only in terms of the number of protein-coding genes; the epigenetic influences involving chromatin remodelling and RNA interference and alternative precursor messenger RNA splicing of functional protein-coding transcripts as well as post-translational modifications of proteins increase the diversity and the functionality of the proteome and likely explain the increased complexity. In addition, there has been an explosion of research addressing possible functional roles for the other 98% of the human genome that does not encode proteins. In fact, >90% of the human genome is likely to be transcribed yielding a complex network of overlapping transcripts that include tens of thousands of long RNAs with little or no protein forming capacity; they are collectively called non-coding RNA. This review highlights the fundamental concepts of biological roles of non-coding RNA and their importance in regulation of cellular physiology under disease conditions like cancer.