The Ribonucleic Acids of <i>Crithidia fasciculata</i>*

Morales, Nydia M.; Roberts, John F.

doi:10.1111/j.1550-7408.1978.tb03886.x

“…These cytoplasmic ribosomes have sedimentation coefficients of 80S and dissociate into large and small subunits of 58S to 60S and 40S to 41S. In C. oncopelti, dissociation occurs especially readily when protein synthesis is not occurring or when the concentration of Mg2e is (48,187,188,250). The dissociation is attributed to a "hidden break" (223,250).…”

Section: Cytoplasmic Organellesmentioning

confidence: 99%

Biology and physiology of the lower Trypanosomatidae.

McGhee¹,

Cosgrove²

1980

Microbiological Reviews

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“…These novel RNAs, designated e, f, and g (apparent chain lengths, 240,195, and 135 nucleotides, respectively), have been observed consistently in cold (0 to 5°C) phenol extracts of different preparations of intact C. fasciculata cells, and neither their presence nor their proportions is affected by variations in the isolation procedure, arguing against their generation by spurious ribonuclease cleavage of high-molecularweight RNA. The inference that e, f, and g are structural components of C. fasciculata ribosomes is based on their recovery in amounts equimolar to those of the high-molecular-weight Several of these observations, notably the heat lability of L-rRNA and the unusual electrophoretic mobility of S-rRNA, have been made by others for C. fasciculata (11,25) and the related species, Crithidia oncopelti (34), and indeed are known to be features of the same rRNA's of some other protists (17). However, the occurrence of novel, small RNAs in the C. fasciculata ribosome has not previously been noted.…”

mentioning

confidence: 99%

Unusual pattern of ribonucleic acid components in the ribosome of Crithidia fasciculata, a trypanosomatid protozoan.

Gray¹

1981

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In a previous study from this laboratory, presumptive ribosomal ribonucleic acid (RNA) species were identified in the total cellular RNA directly extracted from intact cells of the trypanosomatid protozoan Crithidia fasciculata (M. W. Gray, Can. J. Biochem. 57:914-926, 1979). The results suggested that the C. fasciculata ribosome might be unusual in containing three novel, low-molecularweight ribosomal RNA components, designated e, f, and g (apparent chain lengths 240, 195, and 135 nucleotides, respectively), in addition to analogs of eucaryotic 5S (species h) and 5.8S (species i) ribosomal RNAs. In the present study, all of the presumptive ribosomal RNAs were indeed found to be associated with purified C. fasciculata ribosomes, and their localization was investigated in subunits produced under different conditions of ribosome dissociation. When ribosomes were dissociated in a high-potium (880 mM K+, 12.5 mM Mg2") medium, species e to i were all found in the large ribosomal subunit, which also contained an additionaL transfer RNA-sized component (speciesj). However, when subunits were prepared in a low-magnesium (60 mM K+, 0.1 mM Mg2+) medium, two of the novel species (e and g) did not remain with the large subunit, but were released, apparently as free RNAs. Control experiments have eliminated the possibility that the small RNAs are generated by quantitative and highly specific (albeit artifactual) ribonuclease cleavage of large ribosomal RNAs during isolation. In terms of RNA composition and dissociation properties, therefore, the ribosome of C. fasciculata is the most "atypical" eucaryotic ribosome yet described. These observations raise interesting questions about the function and evolutionary origin of C. fasciculata ribosomes and about the organization and expression of ribosomal RNA genes in this organism.Most eucaryotic ribosomes conform to a pattern in which the large subunit contains three ribonucleic acid (RNA) components (25 to 28S, or "L-ribosomal RNA [rRNA]"; 5.8S, or "L3-rRNA"; and 5S), whereas the small subunit contains one (17 to 18S, or "S-rRNA") (3). I have recently shown (14) that the rRNA of Crithidia fasciculata, a trypanosomatid protozoan, differs from that of a typical eucaryote in several respects. (i) The L-rRNA (species a) is heat labile, dissociating into two high-molecular-weight components, species c and d (apparent molecular weights, 0.67 x 10' and 0.575 x 106, respectively). (ii) Heat denaturation of C. fasciculata rRNA also releases a small RNA (species i) analogous in this respect to eucaryotic 5.8SrRNA, but which migrates appreciably more slowly than wheat 5.8S rRNA in nondenaturing polyacrylamide gels. (iii) The S-rRNA of C. fasciculata also displays an anomalously slow migration during polyacrylamide gel electrophoresis, so that its apparent molecular weight (0.825 x 106) is substantially greater than that of the S-rRNA ofmost other eucaryotes (typically, this is -0.7 x 106). (iv) In addition to 5S rRNA (species h), three other small RNAs are found in nondenatured C. fascicu...

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“…Several of these observations, notably the heat lability of L-rRNA and the unusual electrophoretic mobility of S-rRNA, have been made by others for C. fasciculata (11,25) and the related species, Crithidia oncopelti (34), and indeed are known to be features of the same rRNA's of some other protists (17). However, the occurrence of novel, small RNAs in the C. fasciculata ribosome has not previously been noted.…”

mentioning

confidence: 95%

Unusual Pattern of Ribonucleic Acid Components in the Ribosome of Crithidia fasciculata, a Trypanosomatid Protozoan

Gray

¹

1981

Molecular and Cellular Biology

14

0

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In a previous study from this laboratory, presumptive ribosomal ribonucleic acid (RNA) species were identified in the total cellular RNA directly extracted from intact cells of the trypanosomatid protozoan Crithidia fasciculata (M. W. Gray, Can. J. Biochem. 57:914-926, 1979). The results suggested that the C. fasciculata ribosome might be unusual in containing three novel, low-molecular-weight ribosomal RNA components, designated e, f, and g (apparent chain lengths 240, 195, and 135 nucleotides, respectively), in addition to analogs of eucaryotic 5S (species h) and 5.8S (species i) ribosomal RNAs. In the present study, all of the presumptive ribosomal RNAs were indeed found to be associated with purified C. fasciculata ribosomes, and their localization was investigated in subunits produced under different conditions of ribosome dissociation. When ribosomes were dissociated in a high-potassium (880 mM K+, 12.5 mM Mg2+) medium, species e to i were all found in the large ribosomal subunit, which also contained an additional, transfer RNA-sized component (species j). However, when subunits were prepared in a low-magnesium (60 mM K+, 0.1 mM Mg2+) medium, two of the novel species (e and g) did not remain with the large subunit, but were released, apparently as free RNAs. Control experiments have eliminated the possibility that the small RNAs are generated by quantitative and highly specific (albeit artifactual) ribonuclease cleavage of large ribosomal RNAs during isolation. In terms of RNA composition and dissociation properties, therefore, the ribosome of C. fasciculata is the most "atypical" eucaryotic ribosome yet described. These observations raise interesting questions about the function and evolutionary origin of C. fasciculata ribosomes and about the organization and expression of ribosomal RNA genes in this organism.

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The Ribonucleic Acids of *Crithidia fasciculata**

Cited by 9 publications

References 19 publications

Biology and physiology of the lower Trypanosomatidae.

Biology and physiology of the lower Trypanosomatidae.

Unusual pattern of ribonucleic acid components in the ribosome of Crithidia fasciculata, a trypanosomatid protozoan.

Unusual Pattern of Ribonucleic Acid Components in the Ribosome of Crithidia fasciculata, a Trypanosomatid Protozoan

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The Ribonucleic Acids of Crithidia fasciculata*

Cited by 9 publications

References 19 publications

Biology and physiology of the lower Trypanosomatidae.

Biology and physiology of the lower Trypanosomatidae.

Unusual pattern of ribonucleic acid components in the ribosome of Crithidia fasciculata, a trypanosomatid protozoan.

Unusual Pattern of Ribonucleic Acid Components in the Ribosome of Crithidia fasciculata, a Trypanosomatid Protozoan

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The Ribonucleic Acids of *Crithidia fasciculata**