The inhibition of ribosomal RNA (rRNA) maturation by 5-fluorouridine (FUrd) in Novikoff hepatoma cells appears to depend upon the incorporation of the analog into the 45 S rRNA precursor. Precursor synthesized in the presence of FUrd is not processed into mature rRNA, but precursor synthesized in the absence of the analog is processed normally after the addition of the drug. The effect of FUrd ...

Sequence analysis of domains 3 and 4 of 23S rRNA from Pseudomonas fluorescens Ag1 was carried out to allow the design of a strain-specific rRNA oligonucleotide probe targeting this strain. The specificity of the probe, Ps-Ag1, was assessed by dot blot analysis and whole-cell hybridization, and it was found to be specific for P. fluorescens Ag1. The correlation between the ribosomal content of P...

Genetic manipulations have revealed the functions of RNA helicases in ribosomal RNA (rRNA) biogenesis in yeast. However, no report shows the role of an RNA helicase in rRNA formation in higher eukaryotes. This study reports the functional characterization of the frog homologue of nucleolar RNA helicase II/Gu (xGu or DDX21). Down-regulation of xGu in Xenopus laevis oocyte using an antisense olig...

In eukaryotes, scores of excess ribosomal RNA (rRNA) genes are silenced by repressive chromatin modifications. Given the near sequence identity of rRNA genes within a species, it is unclear how specific rRNA genes are reproducibly chosen for silencing. Using Arabidopsis thaliana ecotype (strain) Col-0, a systematic search identified sequence polymorphisms that differ between active and developm...

In eukaryotic cells, ribosomal RNA (rRNA) gene is transcribed by RNA polymerase I (pol I) in the nucleolus as a large (40 S-47 S) precursor RNA (pre-rRNA) (for reviews, see refs. [1,2]). The mature rRNA species (28 S, 18 S and 5.8 S) are formed after a series of specific endonucleolytic cleavage reactions (for a review, see ref. [3]). The rRNA gene (rDNA) is highly reiterated and is arranged in...

Ribosome biogenesis is a fundamental and tightly regulated cellular process, including synthesis, processing, and assembly of rRNAs with ribosomal proteins. Protein arginine methyltransferases (PRMTs) have been implicated in many important biological processes, such as ribosome biogenesis. Two alternative precursor rRNA (pre-rRNA) processing pathways coexist in yeast and mammals; however, how P...

ENP1 is an essential Saccharomyces cerevisiae gene encoding a 483 amino acid polypeptide. Enp1 protein is localized in the nucleus and concentrated in the nucleolus. An enp1-1 temperature-sensitive mutant inhibited 35S pre-rRNA early processing at sites A(0), A(1) and A(2) as shown by northern analysis of steady state levels of rRNA precursors. Pulse-chase analysis further revealed that the enp...

The genes encoding 18S, 5.8S, and 28S ribosomal RNA (rRNA) are tandemly repeated at the nucleolus organizer region (NOR). The NORs in the chicken map to one pair of microchromosomes. A line of chickens that contains individuals that are either disomic, trisomic, or tetrasomic for this chromosome, and have two, three, or four nucleoli and NORs, per cell, respectively, has been described previous...

The loop of a stem structure close to the 5' end of the 18S rRNA is complementary to the box A region of the U3 small nucleolar RNA (snoRNA). Substitution of the 18S loop nucleotides inhibited pre-rRNA cleavage at site A(1), the 5' end of the 18S rRNA, and at site A(2), located 1.9 kb away in internal transcribed spacer 1. This inhibition was largely suppressed by a compensatory mutation in U3,...