U12 minor spliceosomal RNA is formed from U12 small nuclear (snRNA), together with U4atac

U4atac minor spliceosomal RNA

U4atac minor spliceosomal RNA is a ncRNA which is an essential component of the minor U12-type spliceosome complex. The U12-type spliceosome is required for removal of the rarer class of eukaryotic introns ....

/U6atac

U6atac minor spliceosomal RNA

U6atac minor spliceosomal RNA is a non-coding RNA which is an essential component of the minor U12-type spliceosome complex. The U12-type spliceosome is required for removal of the rarer class of eukaryotic introns ....

, U5, and U11 snRNAs and associated proteins, forms a spliceosome

Spliceosome

A spliceosome is a complex of snRNA and protein subunits that removes introns from a transcribed pre-mRNA segment. This process is generally referred to as splicing.-Composition:...

 that cleaves a divergent

Genetic divergence

Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes through time, often after the populations have become reproductively isolated for some period of time...

 class of low-abundance pre-mRNA intron

Intron

An intron is any nucleotide sequence within a gene that is removed by RNA splicing to generate the final mature RNA product of a gene. The term intron refers to both the DNA sequence within a gene, and the corresponding sequence in RNA transcripts. Sequences that are joined together in the final...

s. Although the U12 sequence is very divergent from that of U2, the two are functionally analogous. The predicted secondary structure

Secondary structure

In biochemistry and structural biology, secondary structure is the general three-dimensional form of local segments of biopolymers such as proteins and nucleic acids...

 of U12 RNA is published, but the alternative single hairpin

Stem-loop

Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded DNA or, more commonly, in RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence when read in opposite directions,...

 in the 3' end shown here seems to better match the alignment of divergent Drosophila melanogaster

Drosophila melanogaster

Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...

and Arabidopsis thaliana

Arabidopsis thaliana

Arabidopsis thaliana is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, arabidopsis is popular as a model organism in plant biology and genetics...

sequences.