Table 2. Conservation of donor splice site of U exons.
| Consensus sequence | Donor splice site | |||||||
|---|---|---|---|---|---|---|---|---|
| C35 | A62 | G77 | g100 | t100 | a60 | a74 | g84 | |
| U1 | A | A | G | g | t | c | a | g |
| U2 | A | A | G | g | t | c | a | g |
| U3 | A | A | G | g | t | c | a | g |
| U4 | A | A | A | g | t | c | a | g |
| U5 | A | A | G | g | t | c | a | g |
| U6 | A | A | G | g | t | c | a | g |
| U7 | A | A | G | g | t | t | a | g |
| U8 | A | A | G | g | t | c | a | g |
| U9 | A | A | G | g | t | c | a | g |
| Pseudo-Ua | A | A | G | c | a | c | a | g |
| Pseudo-Ub | A | A | G | c | a | c | a | g |
The numbers given for the consensus sequence nucleotides specify the frequency of occurrence (%). Upper and lower case letters represent exonic and intronic nucleotides, respectively. Highly conserved nucleotides are shown in bold. The exons designated pseudo-Ua and-Ub, despite their homology to U exons, do not have splice donor consensus sequences and are unlikely to serve as transcription initiation sites.