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Reference.org
Long non-coding RNA
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<p>Long non-coding RNAs (long ncRNAs, lncRNA) are a type of <a href="/facts/RNA/HxPeNfNj">RNA</a>, generally defined as <a href="/facts/Transcription_(genetics)/bDgp9HDN">transcripts</a> more than 200 <a href="/facts/Nucleotide/pQKEwlJI">nucleotides</a> that are not translated into protein. This arbitrary limit distinguishes long ncRNAs from small <a href="/facts/Non-coding_RNA/aXqyV5so">non-coding RNAs</a>, such as <a href="/facts/MicroRNA/UjqbYYpe">microRNAs</a> (miRNAs), <a href="/facts/Small_interfering_RNA/891ytkD9">small interfering RNAs</a> (siRNAs), <a href="/facts/Piwi-interacting_RNA/5JXza7t8">Piwi-interacting RNAs</a> (piRNAs), <a href="/facts/SnoRNA/lcWShLfJ">small nucleolar RNAs</a> (snoRNAs), and other short RNAs. Given that some lncRNAs have been reported to have the potential to encode small proteins or micro-peptides, the latest definition of lncRNA is a class of transcripts of over 200 nucleotides that have no or limited coding capacity. However, John S. Mattick and colleagues suggested to change definition of long non-coding RNAs to transcripts more than 500 nt, which are mostly generated by Pol II. That means that question of lncRNA exact definition is still under discussion in the field. Long intervening/intergenic noncoding RNAs (lincRNAs) are sequences of transcripts that do not overlap protein-coding genes. </p><p>Long non-coding RNAs include intergenic lincRNAs, intronic ncRNAs, and sense and antisense lncRNAs, each type showing different genomic positions in relation to <a href="/facts/Gene/e1swwPY6">genes</a> and <a href="/facts/Exon/8KWJtLuN">exons</a>. </p><p>The definition of lncRNAs differs from that of other RNAs such as siRNAs, mRNAs, miRNAs, and snoRNAs because it is not connected to the function of the RNA. A lncRNA is any transcript that is not one of the other well-characterized RNAs and is longer than 200-500 nucleotides. Some scientists think that most lncRNAs do not have a biologically relevant function because they are transcripts of <a href="/facts/Junk_DNA/zyTU8q8M">junk DNA</a>. </p>