Gateway role for rRNA precursors in ribosome assembly.

In Escherichia coli, rRNAs are initially transcribed with precursor sequences, which are subsequently removed through processing reactions. To investigate the role of precursor sequences, we analyzed ribosome assembly in strains containing mutations in the processing RNases. We observed that defects in 23S rRNA processing resulted in an accumulation of ribosomal subunits and caused a significant delay in ribosome assembly.

Role of precursor sequences in the ordered maturation of E. coli 23S ribosomal RNA.

The maturation of ribosomal RNAs (rRNAs) is an important but incompletely understood process required for rRNAs to become functional. In order to determine the enzymes responsible for initiating 3' end maturation of 23S rRNA in Escherichia coli, we analyzed a number of strains lacking different combinations of 3' to 5' exo-RNases. Through these analyses, we identified RNase PH as a key effector of 3' end maturation.

Coordinated regulation of 23S rRNA maturation in Escherichia coli.

In Escherichia coli, rRNAs are transcribed as precursors and require processing at the 3' and 5' ends to generate mature RNA molecules. The largest of these RNAs, 23S rRNA, is matured at the 3' end by a set of exonucleases and at the 5' end by an unknown RNase. Whether the 3' and 5' maturation steps occur independently or are coupled has previously been unclear.

Functional defects in transfer RNAs lead to the accumulation of ribosomal RNA precursors.

Normal expression and function of transfer RNA (tRNA) are of paramount importance for translation. In this study, we show that tRNA defects are also associated with increased levels of immature ribosomal RNA (rRNA). This association was first shown in detail for a mutant strain that underproduces tRNA(Arg2) in which unprocessed 16S and 23S rRNA levels were increased several-fold.

The pseudouridine synthase RluD is required for normal ribosome assembly and function in Escherichia coli.

RluD is the pseudouridine synthase responsible for the formation of Psi1911, Psi1915, and Psi1917 in Escherichia coli 23S rRNA. Previous work from our laboratory demonstrated that disruption of the rluD gene and/or loss of the pseudouridine residues for which it is responsible resulted in a severe growth phenotype. In the current work we have examined further the effect of the loss of the RluD protein and its product pseudouridine residues in a deletion strain lacking the rluD gene.