Ribonucleoproteins in Archaeal Pre-rRNA Processing and Modification

Table 1

Ribosomal RNA (rRNA) and rRNA processing across the three domains.

	Archaea	Eukarya	Bacteria
rRNAs	23S, 5S (LSU); 16S (SSU)	28S, 5.8S, 5S (LSU); 18S (SSU)	23S, 5S (LSU); 16S (SSU)
Ribosome	70S	80S	70S
Large subunit (LSU)	50S	60S	50S
Small subunit (SSU)	30S	40S	30S
Presence of introns in rDNA genes?	In some species [20–24]	In some species	Rare* [25]
Main rRNA modifying machines	sRNPs [26–28]	snoRNPs [29–33]	Site-specific protein enzymes [34, 35]
Number of rRNA Nms and Ψs	S. solfataricus: ~76 [36]	Yeast: 99; Human: 202 [34, 37–40]	E. coli: 14 [34, 37, 38, 40, 41]
Number of C/D and H/ACA s(no)RNAs	S. solfataricus: ~9–17 [42, 43]	Yeast: 75; Human: 207 [40]	0 [34, 35]

∗Uncultured giant sulfur bacteria, such as Thiomargarita namibiensis, have been shown to contain self-splicing introns, varying in number and size, in the 16S rRNA gene. To date, this has been the only report of bacterial rDNA genes containing introns.