A brief introduction of noncoding RNA research

Abstract

RNAs are products of transcription with DNA as their template. In early days of molecular biology and as suggested in the central dogma, RNAs had been viewed as information carrier to transfer genetic information from DNA to functional proteins. This is true for those RNAs discovered earlier by biologists such as mRNAs, rRNAs, tRNAs, snRNAs, and etc. mRNAs are template of translation to give rise to proteins, whereas snRNAs, rRNAs, tRNAs, and some other noncoding RNAs (ncRNAs) are either directly responsible for the correct produce of mRNAs or essential molecules in the process of protein translation. Starting around the last decade of the 21st century and continuing in this century, biologists have increasingly realized that a great number of diverse ncRNAs are present in cells, and they are versatile molecules but not essential for the information flow suggested by the central dogma. RNAs were presumbly precursor molecules in first life forms on earth, as proposed in the RNA world hypothesis. Over the period of evolutionary time, the genetic information was stored in more stable DNA, while most catalytic and structural functions were handed over to more versatile proteins. Some RNAs still function as essential enzymes in current life forms, and a lot RNAs function as intermediates between genes and proteins. On the other hand, pervasive transcription of eukaryotic genome generates abundant ncRNAs. Accuminating findings demonstrate that a lot of ncRNAs are critical regulators in a plethora of life events, which also suggests that ncRNAs may be one of major driving forces in the evolution of life. The first wave in ncRNA studies is on small noncoding RNAs, e.g. microRNAs and piRNAs; then the field of long noncoding RNAs emerges. It has become one of the focuses of modern biology to know the inventroy, functions, functional mechanisms, physiological significances, ecological roles, relevance to inheritance, and involvement in evolution of ncRNAs. Here we briefly introduce our current understandings about categories of ncRNAs. An enormous number of small, long, and more recently circular, ncRNAs are identified in eukaryotic cells. They function in the cytoplasm, in the nucleus, intercellularly, or even interspecies, with a great variety of mechanisms. We have a concise summary about their roles in physiology, inheritance, evolution, and ecology. NcRNAs generally function through interacting with proteins, DNA, or other RNAs (coding or noncoding). We also have a short disscussion about biotechnologies and biomedical applications derived from ncRNAs. It is speculated that more ncRNA catagories (or subtypes, or novel members of known catagory) will be identified in the future. New roles and functional mechanisms will also be uncovered. Great progresses have been made in the field of ncRNAs, and to decipher ncRNAs will undoubtedly remain to be a significant area of research for the coming decades, which would eventually answer the question of “what roles do different forms of RNA play in genome function”.