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. 2021 Sep 16;9:680713. doi: 10.3389/fcell.2021.680713

FIGURE 1.

FIGURE 1

Schematic diagram of representative lncRNA categories. Based on the location of lncRNAs relative to adjacent protein-coding genes, lncRNAs can be classified as: (A) Sense. Transcribed from the sense strand of protein-coding genes, can be considered as transcription variants of protein-coding mRNAs, which usually overlap exons by sharing the same promoter (Ma et al., 2013). (B) Antisense. Transcribed from the antisense strand of protein-coding genes, overlapping with protein-coding genes or covering the entire protein-coding sequence through intron. (C) Intergenic. Also known as long intergenic non-coding RNAs (lincRNAs), transcribed between two protein-coding genes, and located distant from other genes (Schmitz et al., 2016). (D) Intronic. Transcribed from introns of protein-coding genes in either sense or antisense orientation. (E) Bidirectional. Transcribed in the opposite direction of the protein-coding gene promotor within 1 kb.