The U12-type spliceosome is required for removal of the rarer class of eukaryotic introns (AT-AC, U12-type).

[1] U4atac snRNA is proposed to form a base-paired complex with another spliceosomal RNA U6atac via two stem loop regions.

[2] U4atac also contains a 3' Sm protein binding site which has been shown to be essential for splicing activity.

[2] The Drosophila U4atac snRNA has an additional predicted 3' stem loop terminal to the Sm binding site.

[3] It has been shown that mutations in the U4atac snRNA can cause microcephalic osteodysplastic primordial dwarfism type I (MOPD I), also called Taybi-Linder syndrome (TALS).