Eukaryotic nuclear RNase P: structures and functions.
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Base Sequence↗
Biomedical subjects
A J Tranguch
Publications and source records attributed to A J Tranguch.
Analysis of conserved positions in nuclear RNase P RNA.
Secondary structure models of eubacterial and eukaryotic nuclear RNase P RNA subunits show extensive structural similarities, allowing the identification of highly conserved nucleotide positions and molecular modeling of the enzyme-substrate complex in three dimensions. Based on this information, we present a preliminary tertiary structure model of the yeast nuclear RNase P RNA. In addition, the most conserved positions in the structure have been subjected to sequence randomization, with viable sequence variations identified by selection in vivo and characterized for phenotypic consequences.
Base Sequence↗
Structure-sensitive RNA footprinting of yeast nuclear ribonuclease P.
Several enzymatic and chemical reagents were used to probe the secondary structure of Saccharomyces cerevisiae nuclear RNase P RNA in the presence and absence of its protein components. Double-stranded regions were detected with RNase V1 and single-stranded regions with RNase ONE (Escherichia coli RNase I). Nucleotides not paired at Watson-Crick positions were monitored with dimethyl sulfate, kethoxal, and 1-cyclohexyl-3-[2-(N-methylmorpholinio)ethyl]carbodiimide p-toluenesulfonate. The results supported most aspects of the previously proposed, phylogenetically-derived RNA secondary structure, although minor refinements allowed incorporation of both the biochemical and phylogenetic data. Digestion of the RNase P protein(s) with proteinase K gave enhanced reactivities to structure probes at selected positions, indicating regions of the RNA made inaccessible by the presence of the protein subunit(s). The regions of RNA protected in the yeast nuclear holoenzyme were considerably more extensive than that seen in the Escherichia coli holoenzyme, consistent with the observation that the protein moiety generally comprises a larger percentage of the RNase P holoenzyme in eukaryotes than in eubacteria.
Base Composition↗
Replacement of the Saccharomyces cerevisiae RPR1 gene with heterologous RNase P RNA genes.
Phylogenetic studies of yeast nuclear RNase P RNA genes have shown a striking conservation of secondary structure for the Saccharomyces and Schizosaccharomyces RNase P RNAs, yet much of the primary sequence and many substructures vary among the RNAs examined. To investigate which sequences and structural features can be varied and still allow function in a heterologous organism, RNase P genes from several yeast species were tested for the ability to substitute for the Saccharomyces cerevisiae RNA. The RNase P genes from Saccharomyces carlsbergensis and Saccharomyces kluyveri could act as the sole source of RNase P RNA within S. cerevisiae cells, whereas the genes from Saccharomyces globosus and Schizosaccharomyces pombe could not. Although heterologous RNase P RNAs were synthesized by the cells in all cases, the RNAs that complemented tended to be processed from longer precursor transcripts into mature-sized RNase P RNA, while the RNAs that did not complement tended to accumulate as the longer precursor form. The results identified sequences and structures in the RNA that are not essential for interaction with species-specific proteins, processing or localization, and suggested other positions that may be candidates for such processes.
Base Sequence↗
Comparative structural analysis of nuclear RNase P RNAs from yeast.
Secondary structure models for yeast nuclear RNase P RNAs were derived by phylogenetic comparative analysis. RNase P RNA genes from six Saccharomyces species were characterized and compared with the published gene sequences of Saccharomyces cerevisiae (RPR1), Schizosaccharomyces pombe, and Schizosaccharomyces octosporus. The general organization of the Saccharomyces genes were similar: all were present in single copy and contained RNA polymerase III-specific regulatory elements, including tRNA gene-like A- and B-box promoters located within 5' leader regions and poly(T) terminators following the mature RNA domain. As observed previously, two RNase P RNAs were present in each of the species: a shorter RNA corresponding to the mature domain and a longer possible precursor RNA that includes the 5' leader sequences. The mature RNA domains of three of these genes were sufficiently divergent from the S. cerevisiae RNA such that compensatory base changes in paired elements were readily identified, yet homologous regions could be aligned. A striking common core of primary and secondary structure emerged for the Saccharomyces RNase P RNAs. Furthermore, the Schizosaccharomyces homologs conformed in large part to the Saccharomyces conserved core and shared with it a distinctive structural domain that has so far only been observed in the yeast nuclear RNase P RNAs. Comparison of the yeast core to a previously published eubacterial conserved core and to the RNA homologs from vertebrates revealed a number of similarities, suggesting that RNase P RNA from diverse sources may share a core of structurally conserved elements.
Base Sequence↗
Increased expression of biodegradative threonine dehydratase of Escherichia coli by DNA gyrase inhibitors.
The synthesis of inducible biodegradative threonine dehydratase of Escherichia coli increased several-fold in the presence of the DNA gyrase inhibitors, nalidixic acid and coumermycin. Temperature-sensitive gyrB mutants expressed higher levels of dehydratase as compared to an isogenic gyrB+ strain. Immunoblotting experiments showed increased synthesis of the dehydratase protein in the presence of gyrase inhibitors; addition of rifampicin and chloramphenicol to cells actively synthesizing enzyme preventing new enzyme production. Increased expression of dehydratase by gyrase inhibitors was accompanied by relaxation of supercoiled DNA.
Aminocoumarins↗
Structure-function analysis in nuclear RNase P RNA.
Eukaryotic ribonuclease P (RNase P) enzymes require both RNA and protein subunits for activity in vivo and in vitro. We have undertaken an analysis of the complex RNA subunit of the nuclear holoenzyme in an effort to understand its structure and its similarities to and differences from the bacterial ribozymes. Phylogenetic analysis, structure-sensitive RNA footprinting, and directed mutagenesis reveal conserved secondary and tertiary structures with both strong similarities to the bacterial consensus and distinctive features. The effects of mutations in the most highly conserved positions are being used to dissect the functions of individual subdomains.
Bacteria↗