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. 2019 May 14;28(19):3188–3198. doi: 10.1093/hmg/ddz144

Figure 1.

Figure 1

Human PIK3CD mRNA transcripts. (A) PIK3CD protein coding sequence (exons 1–22) are preceded by alternative 5' UTRs. mRNA sequences generally contain two 5' UTR exons (exon -2A, -2B, -2C, or -2D and exon -1; 2e not shown). Some transcripts contain an alternative exon -1 (Alt1, arrow), either as the sole leader exon or following exon -2A. Data derived from Whitehead et al (4), the Ensembl database, and cloning experiments described here. (B) PIK3CD-AS1 and PIK3CD-AS2 are recently identified lncRNAs located antisense to the upstream 5' UTR region of the PIK3CD gene. (C) The P37 transcript is formed by use of an alternative splice site between Exons 3 and 4 that includes intronic sequence immediately downstream of Exon 3 (termed Exon 3A), resulting in a frame shift that introduces a premature stop codon within Exon 4. The resulting product, p37δ, is a truncated protein lacking the kinase domain of full-length p110δ. The 5' UTR exon composition of P37 transcripts has not been investigated, although our preliminary data suggest transcripts contain -2A and Alt1. Transcript structure was derived from Refs. (4, 5). Block arrows denote location of PCR primers.