Nuclear RNA Metabolism

Weinberg, Robin A.

doi:10.1146/annurev.bi.42.070173.001553

Cited by 214 publications

(67 citation statements)

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“…Twenty to 40% of the giant heterogeneous nuclear RNA (HnRNA) molecules found in these cells also contain a poly(A) sequence at their 3' end (6,8). Because the poly(A) in the HnRNA is present at the 3' end, it has been suggested that the region of the HnRNA molecule nearest the 3'-end poly(A) is the material precursor of mRNA (7,9,10).…”

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confidence: 99%

Transcription of Polydeoxythymidylate Sequences in the Genome of the Cellular Slime Mold, Dictyostelium discoideum

Jacobson

Firtel

Lodish

1974

Proc. Natl. Acad. Sci. U.S.A.

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Messenger RNA of the cellular slime mold, Dictyostelium discoideum, contains about equimolar amounts of two classes of poly (adenylic acid) [poly(A)]; one is about 25 nucleotides long and the second about 100 nucleotides long. At least half of the messenger RNA molecules contain one sequence each of poly(A)25 and poly(A)soo; both poly(A) sequences are located near the 3' end of messenger RNA, and the kinetics of their appearance on messenger RNA precursor indicates that poly(A)25 is added before poly(A)soo. Dictyostelium nuclear DNA contains 14,000-15,000 sequences of poly(dT)25 which could code for the smaller poly(A) residues. The poly(A),oo must be added post-transcriptionally. The poly(dT)25 sequences are interspersed throughout the genome and may well represent transcription termination regions.Messenger RNA of mammalian cells contains, at the 3' end, a sequence of poly(adenylic acid) [poly(A)] of about 200 bases (1-9). Twenty to 40% of the giant heterogeneous nuclear RNA (HnRNA) molecules found in these cells also contain a poly(A) sequence at their 3' end (6,8). Because the poly(A) in the HnRNA is present at the 3' end, it has been suggested that the region of the HnRNA molecule nearest the 3'-end poly(A) is the material precursor of mRNA (7, 9, 10).There is evidence that these poly(A) sequences are not encoded in DNA, but are added post-transcriptionally: (a) cordycepin blocks synthesis of poly(A) and appearance of mRNA into the cytoplasm, but does not inhibit synthesis of HnRNA (5,7,8,11,12); (b) the number and size of poly(dT) sequences in mammalian nuclear DNA has been determined by isolation of polypyrimidine sequences in DNA after depurination; these poly(dT) sequences could account for only a very small fraction of the poly(A)200 sequences in mRNA (13); and (c) adenovirus type-2 mRNA contains poly(A) sequences of 100-200 bases, yet adenovirus DNA contains no poly(dT) sequences of equivalent size detectable by RNA DNA hybridization (14).We previously showed that mRNA from Dictyostelium contains a poly(A) sequence of 40-150 nucleotides, with a mean size of 100 at the 3' end (15). We report here that mRNA also contains a sequence of poly (A) (15,16). Dictyostelium nuclei were isolated and utilized for cell-free RNA synthesis as described (17).Isolation of Poly(A). Either total RNA, or poly(A)-containing RNA purified by chromatography on poly(U)-Sepharose, was used. RNAs were digested at 370 for 30-60 min in 0.36 M Na+ by 10 units/ml of RNase T, and 5 ,ug/ml of RNase A. Sodium dodecyl sulfate (0.5%) and proteinase K (1 mg/ml) were added to terminate the reaction. After an additional incubation at 300, the mixture was extracted with phenol-chloroform and the poly(A) material was purified by adsorption to and elution from poly(U)-Sepharose or oligo-(dT)-cellulose (15,16). Finally the poly(A) was precipitated with ethanol, with Escherichia coli tRNA as carrier. The size and base composition of the poly(A) sequences were the same whether or not the poly(A)-containing RNA was first purified by chro...

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confidence: 99%

Transcription of Polydeoxythymidylate Sequences in the Genome of the Cellular Slime Mold, Dictyostelium discoideum

Jacobson

Firtel

Lodish

1974

Proc. Natl. Acad. Sci. U.S.A.

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“…The existence of low molecular weight 'cRNA' [44] hybridizing to a relatively large portion of the genome has been observed in a number of laboratories. It is possible the 'cRNA' is composed, to a large extent, of the products of early transcription termination rather than random breakdown products of hnRNA as suggested [45]. At times of active gene expression one might expect a diminution of such abortive transcription and a significant increase in the average length of the primary transcripts.…”

Section: Discussionmentioning

confidence: 97%

Attenuation as a general mechanism for the regulation of differential gene transcription in eukaryotes

Remington¹

1979

FEBS Letters

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“…The discovery that 5-S RNA is synthesized by a nucleoplasmic polymerase [23] gives weight to the hypothesis that genes governing 5-S RNA are localised in the nucleoplasm. The presence of 5-S RNA within the nucleolus at early stages may be due to the experimental conditions, or may be because of the rapid diffusion of 5-S RNA within the cell [24]. Another aspect of these results is the coordination between the rate of appearance of 5-S and "45-S fraction" RNAs in the nucleus of L5178 Y cells.…”

Section: Discussionmentioning

confidence: 99%

“…Nuclear subribosomal particles were isolated from the nucleoplasm (or nuclear supernatant fraction) by centrifugation through a [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] (w/w) sucrose gradient buffered in 0.01 M Tris, 0.5 M NaC1, 0.05 M MgC1, (pH 7.4), in SW25.1 or SW41 rotor of the Spinco model L2 [17]. The method of extracting nucleolar ribonucleoprotein particles has been reported in a previous paper [16].…”

Section: Nuclear-r Ibonucleopro Tein Isolationmentioning

confidence: 99%

5‐S RNA: Biosynthesis and Association to Immature Ribosomal Particles in the Nucleus of Lymphocytic Mouse Leukemia Cells, L5178 Y

Auger

Tiollais

1974

European Journal of Biochemistry

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In the nucleus of L5178 Y cells, a lymphocytic mouse leukemia cell strain, newly synthesized 5-S ribosomal RNA first appears mainly in the nucleoplasm and then diffuses into the nucleolus. Kinetic studies have revealed that the appearance rates of 5-S RNA and "45-S fraction" ribosomal precursor RNA are identical. During the first 30 min, 5-S RNA binds to proteins and constitutes a nuclear pool of independent ribonucleoprotein particles which sediment at approximately 11 S. After this time, it begins to integrate with the nucleolar "80-S nascent" particle. This ribonucleoprotein particle contains "45-S fraction" RNA, the direct product of ribosomal DNA genes and has been shown to represent the first stage of ribosome formation. 5-S RNA remains associated to preribosomal particles during the nuclear maturation process leading to the large ribosomal subunit, located in the cytoplasm. In labeling experiments, the molar ratio of labeled 5-S RNA compared to high-molecular-weight ribosomal RNA in ribonucleoprotein particles, continues to increase until reaching a value of 1 : 1 for steady-state labeling. The association of 5-S RNA to preribosomal particles is more labile than it is to the mature ribosomal subunit. Chemical products such as heparin or sarkosyl used to extract nucleolar ribonucleoprotein particles, were shown to detach 5-S RNA from these particles; but dithiothreitol keeps the particles intact.Among the several types of RNA which make up the ribosomes of mammalian cells, the 5-S RNA is unique in certain of its characteristics. 28-S, 18-S and 7-S RNA are derived from a common precursor, the "45-S fraction" RNA [l], which is transcribed from nucleolar DNA cistrons [2], whereas 5-S RNA seems likely to be transcribed directly into its mature form [3,4], in an extranucleolar site of the nucleus 5-S RNA is found to be present in the large ribosomal subunit in a 1 : l molar ratio with 28-S RNA [7], and its precise function in the biological activity of the ribosome has recently received considerable attention [8 -101. On the other hand, little information about the metabolism of newly synthesized 5-S RNA has as yet been obtained. Knight and Darnell's extensive study [7] established that newly formed 5-S RNA t5,61.is partly associated to the 55-S nucleoplasmic particle, a direct precursor of the large ribosomal subunit, and partly free within the nucleus. Others have detected the presence of 5-S RNA in the nucleolar "55-S particle" containing 32-S RNA, the closest precursor of 28-S RNA [11,12]. Furthermore, Maden [I31 and Darnel1 [14] mention the association of 5-S RNA to the primary particle formed after transcription (80-S nascent particle), but to our knowledge no experimental support of this finding has been published.In the present work, we have attempted to present a kinetic study of the appearance of newly synthesized 5-S RNA in the two subnuclear fractions, nucleolus and nucleoplasm, as well as in nuclear immature ribosomal particles. 5-S RNA was found in a transient pool of low-molecular-weight parti...

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Nuclear RNA Metabolism

Cited by 214 publications

References 0 publications

Transcription of Polydeoxythymidylate Sequences in the Genome of the Cellular Slime Mold, Dictyostelium discoideum

Transcription of Polydeoxythymidylate Sequences in the Genome of the Cellular Slime Mold, Dictyostelium discoideum

Attenuation as a general mechanism for the regulation of differential gene transcription in eukaryotes

5‐S RNA: Biosynthesis and Association to Immature Ribosomal Particles in the Nucleus of Lymphocytic Mouse Leukemia Cells, L5178 Y

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