RNA splicing in archaea requires at least an endonuclease
and a ligase, as is the case for the splicing of eukaryal
nuclear tRNAs. Splicing endonucleases from archaea and
eukarya are homologous, although they differ in subunit
composition and substrate recognition properties. However,
they all produce 2′,3′ cyclic phosphate and
5′-hydroxyl termini. An in vitro-transcribed, partial
intron-deleted Haloferax volcanii elongator tRNAMet
has been used to study splicing by H. volcanii
cell extracts. Substrates and products were analyzed by
nearest neighbor analyses using nuclease P1 and RNase T2,
and fingerprinting analyses using acid-urea gels in the
first dimension and gradient thin layer chromatography
in the second dimension. The results suggest that 2′,3′
cyclic phosphate at the 3′ end of the 5′ exon
is converted into the splice junction phosphate forming
a 3′,5′-phosphodiester linkage. This resembles
the animal cell type systems where the junction phosphate
preexists in the transcript, and differs from yeast type
systems, where GTP is the source of junction phosphate.