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Table 2 Conservation of Drosophila melanogaster U12-type introns in humans.

From: Evolutionary dynamics of U12-type spliceosomal introns

  Annotation symbol Termini Gene symbol (name) in fruitflies and/or in humans Intron number Total number of introns Fruitflies Humans
1 CG6323 GT-AG Tsp97E (Tetraspanin 97E); TSPAN13 (tetraspanin 13) 2 4 U12 U12
2 CG8408 GT-AG TMEM41B (transmembrane protein 41B) 3 3 U12 U12
3 CG17912 GT-AG ZNF207 (Zinc finger protein 207) 1 3 U12 U12
4 CG32705 GT-AG ZDHHC8 (zinc finger, DHHC-type containing 8) 4 11 U12 U12
5 CG33108 GT-AG C19orf54 2 3 U12 U12
6 CG4894 GT-AG Ca-α1D (calcium-channel protein); CACNA1D (calcium channel) 3 31 U12 U12
7 CG7892 GT-AG nmo (nemo); NLK (nemo-like kinase) 6 10 U12 U12
8 CG15735 GT-AG LSM12 1 4 U12 U12
9 CG3294 GT-AG ZRSR2 (zinc finger, RNA-binding motif and serine/arginine rich 2); U2AF (small subunit related protein) 3 4 Twintron U2 only
10 CG16941 GC-AG SF3A1 (splicing factor 3a, subunit 1, 120 kDa) 1 6 U12 absent
11 CG11839 AT-AC CCDC16 (coiled-coil domain containing 16); ZNF830 (zinc finger protein 830) 1 1 U12 absent
12 CG11328 AT-AC Nhe3; SLC9A7 (solute carrier family 9) 5 12 U12 U12
13 CG18177 AT-AC FLJ14154 hypothetical protein 4 4 U12 U12
14 CG7736 AT-AC Syx6 (Syntaxin 6); STX6 (syntaxin 6) 1 2 U12 U12
15 CG17228 AT-AC pros (prospero); PROX1 (prospero homeobox 1) 2 4 Twintron U12
16 CG15081 AT-AC l(2)03709 (lethal (2) 03709); PHB2 (prohibitin 2) 3 5 U12 U12
17 CG3427 AT-AC Epac; RAPGEF3 (Rap guanine nucleotide exchange factor 3) 11 16 U12 U12
18 CG11984 AT-AC KCMF1 (potassium channel modulatory factor 1) 3 6 U12 U12
19 CG15589 AT-AC Ca-alphaT-RC (Voltage-dependent T-type calcium channel) 1 23 U12 U12
  1. Depending on the terminal dinucleotides, or termini, U12-type introns are divided into two major subtypes. Of the nineteen fruit fly U12-type introns, ten are GT-AG subtype, including one GC-AG and eight AT-AC. Sixteen have U12-type ortholog in humans. These sixteen human orthologous U12-type introns are of the same subtype as their fruitfly ortholog. The absence of the U12-type intron in the human SF3A1 gene is likely an intron deletion after insects diverged. The CCDC16 gene is intronless in mammals and fish but not in chickens and frogs. Thus, the absence of the U12-type intron in the human CCDC16 gene is presumably due to a retroposition of the gene that occurred in early mammals. The third intron of the fruit fly CG3294 (URP) gene has two pairs of splice sites that form two alternative spliced introns, one of the U12-type and one of the U2-type. The pair of U12-type splice sites is absent in non-diptera species.