RNA longo não-codificante: características, mecanismos e funcionalidade do DNA"lixo".

Abstract

At the beginning of the 90´s decade a noncoding RNA was found when they the aim was to find new protein coding genes. The noncoding RNAs can be grouped into major classes: small noncoding RNAs, and long noncoding RNAs. Nowadays, there is no clear definition for long noncoding RNAs (lncRNAs) based on biological premises. Thousands of noncoding RNAs are transcribed from mammal´s genome. Up to ninety percent of the human genome is transcribed, however it is not known if all these transcripts are functional. Long noncoding RNA´s biogenesis is similar to the protein coding RNAs, mostly of them are transcribed by RNA Polymerase II and some by RNA Polymerase III. It was suggested a classification system, in which the relative position of lncRNAs to protein coding regions is taken into account, and it has been used since then. LncRNAs can function in several different ways, so far these molecules were described acting as: (a) guide; (b) chromatin modifiers, by interaction with DNA associated protein; (c) transcriptional regulators, affecting RNA polymerase interactions e transcription factors; (d) scaffolds, recruiting multiple protein forming a ribonucleoprotein complex; and (e) decoy. LncRNAs can exert their functional role at transcriptional and post-transcription levels, including as a chromatin modifier, transcriptional factors coactivator, decay of mRNAs, among others. Although there are only a few well documented lncRNAs, studies made só far suggest that lncRNAs may be related to almost all levels of gene expression regulation, demonstrating how important is the study of these molecules. In this review, we aim to gather the main lncRNAs biological characteristics and functional mechanisms.