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Page 4 of 23 Parsons et al. J Cancer Metastasis Treat 2018;4:19 I http://dx.doi.org/10.20517/2394-4722.2018.11

Figure 1. lncRNAs derive from a number of genetic loci and associate with specific lncRNA function. (A) pa-lncRNAs originate from a
bi-directional promoter from the sense strand of gene foci. These lncRNAs tend to operate in cis and regulate the neighboring protein
coding gene; (B) ea-lncRNAs are similar to pa-lncRNAs yet are transcribed from enhancer regions within the genome; (C) NAT-lncRNAs
are transcribed from the antisense strand and contain fully or partially complementary sequences to sense-strand transcripts, depending
upon the surrounding genetic elements that regulate transcription of NATs; (D) gb-lncRNAs are transcribed in sense orientation, typically
are one exon in length, and could share exons from protein coding transcripts; (E) lincRNAs are transcribed from genetic loci in either
sense or antisense fashion and span regions considered transcriptionally active, coding or otherwise. Portions of this figure were adapted
from Martens-Uzunova et al. [229] , with permission

when lost in mice perturbs the development of cardiomyocytes indicating Bvht is an important regulator of
mammalian cardiac development [67,68] .

Natural antisense transcripts (NATs) are considered full length RNA transcripts initiated on the antisense
strand of a respective protein coding gene [69,70] . Given this type of lncRNA has high complementarity to
the mRNA transcript deriving from the sense strand, the formation of localized RNA duplexes results in
enhanced RNA stability through HuR binding, or degradation via activation of RNA interference (RNAi)
pathways. HIF1A-AS2, for instance, is transcribed from the HIF1A locus and operates as a scaffold,
recruiting chromatin remodeling complexes, as well as RBPs such as IGF2BP2 to distinct genetic loci .
[71]