Unexpected diversity of RNase P, an ancient tRNA processing enzyme: Challenges and prospects

RNase P is an essential tRNA-processing enzyme in all domains of life. We identified an unknown type of protein-only RNase P in the hyperthermophilic bacterium Aquifex aeolicus: Without an RNA subunit and the smallest of its kind, the 23-kDa polypeptide comprises a metallonuclease domain only. The protein has RNase P activity in vitro and rescued the growth of Escherichia coli and Saccharomyces cerevisiae strains with inactivations of their more complex and larger endogenous ribonucleoprotein RNase P. Homologs of Aquifex RNase P (HARP) were identified in many Archaea and some Bacteria, of which all Archaea and most Bacteria also encode an RNA-based RNase P; activity of both RNase P forms from the same bacterium or archaeon could be verified in two selected cases. Bioinformatic analyses suggest that A. aeolicus and related Aquificaceae likely acquired HARP by horizontal gene transfer from an archaeon.

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Basic Domains Target Protein Subunits of the RNase MRP Complex to the Nucleolus Independently of Complex Association

Molecular Biology of the Cell ◽

10.1091/mbc.12.11.3680 ◽

2001 ◽

Vol 12 (11) ◽

pp. 3680-3689 ◽

Cited By ~ 15

Author(s):

Hans van Eenennaam ◽

Annemarie van der Heijden ◽

Rolf J. R. J. Janssen ◽

Walther J. van Venrooij ◽

Ger J. M. Pruijn

Keyword(s):

Protein Composition ◽

Rnase P ◽

Nucleolar Localization ◽

Rrna Processing ◽

Protein Subunits ◽

Trna Processing ◽

Rnase Mrp ◽

Human Rnase ◽

The Difference ◽

Active Transport Process

The RNase MRP and RNase P ribonucleoprotein particles both function as endoribonucleases, have a similar RNA component, and share several protein subunits. RNase MRP has been implicated in pre-rRNA processing and mitochondrial DNA replication, whereas RNase P functions in pre-tRNA processing. Both RNase MRP and RNase P accumulate in the nucleolus of eukaryotic cells. In this report we show that for three protein subunits of the RNase MRP complex (hPop1, hPop4, and Rpp38) basic domains are responsible for their nucleolar accumulation and that they are able to accumulate in the nucleolus independently of their association with the RNase MRP and RNase P complexes. We also show that certain mutants of hPop4 accumulate in the Cajal bodies, suggesting that hPop4 traverses through these bodies to the nucleolus. Furthermore, we characterized a deletion mutant of Rpp38 that preferentially associates with the RNase MRP complex, giving a first clue about the difference in protein composition of the human RNase MRP and RNase P complexes. On the basis of all available data on nucleolar localization sequences, we hypothesize that nucleolar accumulation of proteins containing basic domains proceeds by diffusion and retention rather than by an active transport process. The existence of nucleolar localization sequences is discussed.

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Characterization of conserved sequence elements in eukaryotic RNase P RNA reveals roles in holoenzyme assembly and tRNA processing

RNA ◽

10.1261/rna.7282205 ◽

2005 ◽

Vol 11 (6) ◽

pp. 885-896 ◽

Cited By ~ 7

Author(s):

S. XIAO

Keyword(s):

Rnase P ◽

Trna Processing ◽

Conserved Sequence ◽

Sequence Elements

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Proteasome Mutants, pre4-2 and ump1-2, Suppress the Essential Function but Not the Mitochondrial RNase P Function of the Saccharomyces cerevisiae Gene RPM2

Genetics ◽

10.1093/genetics/154.3.1013 ◽

2000 ◽

Vol 154 (3) ◽

pp. 1013-1023 ◽

Cited By ~ 1

Author(s):

Mallory S Lutz ◽

Steven R Ellis ◽

Nancy C Martin

Keyword(s):

Saccharomyces Cerevisiae ◽

Essential Gene ◽

Carbon Sources ◽

Growth Arrest ◽

Nuclear Gene ◽

Rnase P ◽

20S Proteasome ◽

Mitochondrial Trna ◽

Additional Function ◽

Trna Processing

Abstract The Saccharomyces cerevisiae nuclear gene RPM2 encodes a component of the mitochondrial tRNA-processing enzyme RNase P. Cells grown on fermentable carbon sources do not require mitochondrial tRNA processing activity, but still require RPM2, indicating an additional function for the Rpm2 protein. RPM2-null cells arrest after 25 generations on fermentable media. Spontaneous mutations that suppress arrest occur with a frequency of ~9 × 10−6. The resultant mutants do not grow on nonfermentable carbon sources. We identified two loci responsible for this suppression, which encode proteins that influence proteasome function or assembly. PRE4 is an essential gene encoding the β-7 subunit of the 20S proteasome core. A Val-to-Phe substitution within a highly conserved region of Pre4p that disrupts proteasome function suppresses the growth arrest of RPM2-null cells on fermentable media. The other locus, UMP1, encodes a chaperone involved in 20S proteasome assembly. A nonsense mutation in UMP1 also disrupts proteasome function and suppresses Δrpm2 growth arrest. In an RPM2 wild-type background, pre4-2 and ump1-2 strains fail to grow at restrictive temperatures on nonfermentable carbon sources. These data link proteasome activity with Rpm2p and mitochondrial function.

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