To elucidate the molecular mechanism by which the potent anticancer drug, 5-fluorouracil (5-FUra), inhibits cell proliferation, the effect of its metabolite, 5-fluorouridine triphosphate, on transcription of rat rRNA gene and processing of pre-rRNA was investigated in S-100 extract from the mouse lymphosarcoma cells. The in vitro processing of pre-rRNA substrate synthesized from the T3 promoter...

In eukaryotes, each of the more than 100 copies of ribosomal RNA (rRNA) genes exists in either an RNA polymerase I transcribed open chromatin state or a nucleosomal, closed chromatin state. Open rRNA genes guarantee the cell's supply with structural components of the ribosome, whereas closed rRNA genes ensure genomic integrity. We report that the observed balance between open and closed rRNA ge...

A cDNA clone that encodes the large subunit of mitochondrial ribosomal RNA (LSU rRNA) from the liver fluke F. hepatica was isolated and characterized. This RNA molecule is polyadenylated at the 3' end and represents 10% of the poly A+RNA in adult F. hepatica. Fluke LSU rRNA has significant sequence homology to mosquito mitochondria LSU rRNA and is more closely related to the mitochondrial rRNA ...

It has become increasingly clear that proper cellular control of pluripotency and differentiation is related to the regulation of rRNA synthesis. To further our understanding of the role that the regulation of rRNA synthesis has in pluripotency we monitored rRNA synthesis during the directed differentiation of human embryonic stem cells (hESCs). We discovered that the rRNA synthesis rate is red...

Correct docking of U3 small nucleolar RNA (snoRNA) on pre-ribosomal RNA (pre-rRNA) is essential for rRNA processing to produce 18S rRNA. In this report, we have used Xenopus oocytes to characterize the structural requirements of the U3 snoRNA 3'-hinge interaction with region E1 of the external transcribed spacer (ETS) of pre-rRNA. This interaction is crucial for docking to initiate rRNA process...

We have previously shown that the 23S rRNA of Salmonella strains is highly fragmented by specific enzyme cleavages. In this article, we report that 23S rRNA of Salmonella strains is rapidly degraded as the cells enter the stationary phase. More than 90% of the 23S rRNA is degraded when the cells reach the stationary phase. The rate of degradation of 23S rRNA correlated with its degree of fragme...

Most eukaryotic C/D small nucleolar RNAs (snoRNAs) guide 2'-O methylation (Nm) on rRNA and are also involved in rRNA processing. The four core proteins that bind C/D snoRNA in Trypanosoma brucei are fibrillarin (NOP1), NOP56, NOP58, and SNU13. Silencing of NOP1 by RNA interference identified rRNA-processing and modification defects that caused lethality. Systematic mapping of 2'-O-methyls on rR...

Streptomyces venezuelae ATCC 10595 harbors seven rRNA gene clusters which can be distinguished by BglII digestion. The three rRNA genes present in each set are closely linked with the general structure 16S-23S-5S. We cloned rrnA and sequenced the 16S-23S spacer region and the region downstream of the 5S rRNA gene. No tRNA gene was found in these regions.

S. coelicolor A3(2) contains six ribosomal RNA operons. Here we describe the cloning of rrnA, rrnC and rrnE, thereby completing the cloning of all operons. Southern hybridisation of genomic DNA with a heterologous probe from the E.coli rrnB 16S rRNA gene showed differences in hybridisation among the six rRNA operon-containing bands. The nucleotide sequence of the 16S rRNA gene and the upstream ...

The amount of intact 40S rRNA precursor was followed by Northern hybridization in the course of the early embryogenesis of wild-type Xenopus laevis and its anucleolate mutant. The total amount of 40S rRNA precursor did not alter appreciably until the midblastula stage, decreased at the late blastula stage, and then increased. In the anucleolate mutant, in which no rRNA synthesis occurs, the 40S...