S. Potter et al., RIBOSOMAL-RNA PRECURSOR PROCESSING BY A EUKARYOTIC U3 SMALL NUCLEOLARRNA-LIKE MOLECULE IN AN ARCHAEON, Science, 268(5213), 1995, pp. 1056-1060
An RNA-containing endonuclease that catalyzes the excision and maturat
ion of the 16S ribosomal RNA (rRNA) from the rRNA primary transcript (
pre-rRNA) in the hyperthermophilic archaeon Sulfolobus acidocaldarius
has been characterized. The ribonucleoprotein was inactivated by micro
coccal nuclease treatment and inactivation was reversed by reconstitut
ion with bulk RNA. A 159-nucleotide RNA with sequence and structural s
imilarity to U3 small nucleolar RNAs of eukaryotes copurified with the
endonuclease activity. Oligonucleotide-targeted ribonuclease H inacti
vation of the US-like RNA component also abolished processing activity
. A motif within the U3 homolog is complementary to the region around
the three cleavage sites in the pre-RNA substrate. Thus, US-mediated p
rocessing of pre-rRNA is not specific to eukaryotes; its origin predat
es the divergence of archaea and eukaryotes.