Why are minor introns bounded by nucleotides AT-AC, where T is not normally in RNA?
It is not unusual for RNA sequences to be reported with T instead of U; the writer is reporting the cDNA sequence instead of the RNA sequence.  In RNA at the boundary of the minor intron, there is a uracil.  In the following page, the writers follow the oft-used convention of describing RNA with T instead of U (writing the cDNA sequence).  https://en.wikipedia.org/wiki/Minor_spliceosome