Schematic illustrations of principal UGP genomic structures. Each arrow represents one transcribed feature. Only the orientation of the transcribed features is shown. Individual exons of the features are not shown. (A) Three types of exon-to-exon cis-antisense pairs. (Left) A tail-to-tail cis-antisense pair of transcribed features (genes, TUs, or one gene and one TU) on opposite strands in the same locus, with overlap of the last exons (“tails”) of the two features. Only the last exons are involved in the overlap. (Center) A head-to-head cis-antisense pair of transcribed features on opposite strands in the same locus, with overlap of the first exons (“heads”) of the two features. Only the first exons are involved in the overlap. (Right) cis-antisense pairs that are neither tail-to-tail nor head-to-head are collectively referred to as “other” or “complex” in this article. Only one of the many possible configurations of cis-antisense pairs is shown (B) A pair of transcribed features with a putative bidirectional promoter. (C) A gene (gray) that is antisense to multiple other genes (black). (D) A gene (gray) that shares a bidirectional promoter with another gene (solid black) and harbors an antisense transcript (hatched black).
