Question

rRNAs and tRNAs undergo extension base modifications. For rRNAs, what types of modifications occur and how are they introduced?

Answer 1

For r RNAs three types of modifications occurs.

1:~Base methylation

2:~Ribose methylation

3:~Pseudouridylation

Post transcriptional ribosomal RNA modification is the most common in all branches.

1:~Base methylation:~Base methylation modification best conserved in number and positions among all of the species.its conserved with bacteria containing slightly more than 10 commonly found in Eukaryotes.Base methylation occurs in highly coserved rRNA sequence.In prokaryotes small subunits rRNA are not essential but it's improve the proteins translation efficiency.

2:-Riboes methylation:~Riboes methylation for rRNA always occurring at the 2'Hydroxyl position on the sugar.Ribose methylation in sulfobolus solfataricus an arches. And this archea found in eukaryotes.Ribose methyls occurs in highly conserved reasons that are evolutionary reasons of rRNA.Specific positions of methylation among eukaryotes is really very well conserved.Most of the ribose methylation takes place earlier in rRNA processing.Hypothesized with chaperon protein that may add in foldings.None of the signal site of ribose methylation is found to be compulsary and although global rRNA demethylation caused by mutation in the NOP1 protein.

3:-Pseudouridylation:~This type of methylation is numerous in eukaryotes and very few in bacteria and archaea.Studies of eukarotic psi residues showed that they are found in most evolutionary conserved reigons of rRNA.Residues were clustered in three main regions.All are associated with the peptidyl transfer center of ribosome.Residues play an very important role in the ribosome some are undetermined function and some are improving translational efficiency.