Roumanian Biotechnological Letters Vol. 13, No. 6, 2008, pp. 3977-3983 Copyright © 2008 Bucharest University Printed in Romania. All rights reserved Roumanian Society of Biological Sciences MINIREVIEW 3977 microRNA a macro Revolution in Medical Biotechnologies Received for publication, October 2, 2008 Accepted, October 23, 2008 MIHAI BURLIBAŞA 1 , LILIANA BURLIBAŞA 2 , LORELAI BIANCA GAVRILĂ 3 , VALERIA ROSALINDA GAVRILĂ 3 , LUCIAN GAVRILĂ 2 1 University of Medicine and Pharmacy „Carol Davila”, Bucharest, Romania 2 University of Bucharest, Institute of Genetics, Romania No 1-3 Aleea Portocalilor, Sector 6, Bucharest, Romania 3 Corresponding author: e-mail: Toronto University, Canada mburlibasa@gmail.com ; liliana_burlibasa@yahoo.com.au Abstract Over the past decade RNA interference mechanism has emerged as a natural pathway for silencing gene expression. Starting with the field of plant biotechnology in early 90s, our knowledge about RNAi proved presently its enormous potential for engineering the control of gene expression, as well as for its use as a tool in functional genomics. The predominantly practical significance of RNAi is conferred by its application as a therapeutic mechanism. RNAi may yield RNA based drugs to treat human diseases and it proved to be efficient in control of some parasites interaction with their host genome. This article is based on a review of the literature referring to RNA from the PubMed database. Keywords: RNAi, medical biotechnologies, silencing genes A brief history of nucleic acids discoveries awarded with Nobel Prize The genetic material was identified as deoxyribonucleic acid in 1944 [1] and the double-helical nature of DNA was discovered in 1953 by Crick F. C., Watson J. D. and Wilkins M., recipients of the Nobel Prize in Physiology and Medicine, in 1962 [2]. After these landmark discoveries, the main problem for eukaryotes was to elucidate how nuclear DNA could govern protein synthesis in the cytoplasm. In 1961, Jacob F. and Monod J. L. presented a visionary gene control model, known as operon hypothesis, for which they received the Nobel Prize in Physiology and Medicine in 1965 [2]. In their proposed model a gene is transcribed into specific RNA species – messenger RNA (mRNA). Soon afterwards, in 1968, Nirenberg M and Khorana H.G. received the Nobel Prize in Physiology and Medicine for deciphering the genetic code that could assign specific codons (i.e. triplets of nucleotides) to one specific aminoacid from the known natural twenty amino acids. After all these findings RNA was believed to correspond to a continuous nucleotide sequence in the DNA, until Gilbert W. (Nobel Prize in Chemistry, 1980) discovered that in eukaryotes, the gene is a mosaic composed of sequences coding for aminoacids, called exon, which are separated by noncoding sequences that were called introns. In 1977, Sharp P. and Roberts R. (Nobel Prize in 1993) revealed that the mRNA sequence could be distributed discontinuously until it undergoes posttranscriptional processing (i.e. splicing) represented by cleavage and removal of introns followed by rejoining of exons into a mature mRNA. This mature RNA carries to the cytoplasm the genetic message for the polypeptide synthesis inside the ribosomes. The two researchers suggested that the mRNA sequences, the exons, are likely to be cut out from the primary transcript and spliced, while the introns are degraded. From this outstanding finding important evolutionary implications have emerged. In 1989 Altman S.