Fig. 1.

The possible genomic locations of lncRNAs. Protein-coding genes and their exons are represented by green segments, while lncRNAs and their introns are represented by pink segments. (A) An intergenic lncRNA, transcribed from either DNA strand between two protein-coding genes. (B) An intronic lncRNA, transcribed from protein-coding gene introns. (C) A sense lncRNA, transcribed from the sense strand of protein-coding genes, overlapping with part (or entirely) of a protein-coding sequence and one or more introns. (D) An antisense lncRNA, transcribed from the antisense strand of protein-coding genes, overlapping with a part (or entirely) of a protein-coding sequence and 1 or more introns. (*) Sense and Antisense lncRNAs are subcategories of a larger class called genic lncRNAs.