Localization and kinetics of formation of nuclear heterodisperse RNA, cytoplasmic heterodisperse RNA and polyribosome-associated messenger RNA in HeLa cells

Penman, Sheldon; Vesco, Cesare; Penman, Maria

doi:10.1016/0022-2836(68)90234-9

Cited by 576 publications

(195 citation statements)

References 19 publications

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Section: Pre-rrna Processing Factors Are Directly Recruited To Activementioning

confidence: 91%

“…At a very low concentration of 0.04 g/ml, ActD selectively inhibits RNA Pol I activity as a result of the higher G/C contents of the rDNA (Perry, 1963). Nuclear run-on experiments show that rRNA transcription in HeLa cells is reduced to Ͻ1% of its normal level within 1 h of ActD (0.04 g/ml) treatment (Penman et al, 1968; D. Chen and S. Huang, unpublished results).To understand nucleologenesis in the absence of Pol I transcription, we compared the localization of UBF, nucleolin, and fibrillarin throughout mitosis in cells grown in a low concentration of ActD with those grown in drug-free medium. The results demonstrate that the rDNA transcription factor UBF remains associated with competent NORs throughout mitosis and within the newly formed nuclei (Figure 1, C and D) in a similar manner in both treated and nontreated cells (Figure 1, compare A with C and B with D).…”

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confidence: 98%

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Initiation of Nucleolar Assembly Is Independent of RNA Polymerase I Transcription

Dousset

Wang

Verheggen

et al. 2000

MBoC

124

122

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This report examines the distribution of an RNA polymerase I transcription factor (upstream binding factor; UBF), pre-rRNA processing factors (nucleolin and fibrillarin), and pre-rRNAs throughout mitosis and postmitotic nucleologenesis in HeLa cells. The results demonstrate that nucleolin, fibrillarin, and pre-rRNAs synthesized at G2/M phase of the previous cell cycle are directly recruited to UBF-associated nucleolar organizer regions (NORs) early in telophase before chromosome decondensation. Unlike the fusion of prenucleolar bodies to the nucleoli, this early recruitment of processing factors and pre-rRNAs is independent of RNA polymerase I transcription. In the absence of polymerase I transcription, the initial localization of nucleolin, fibrillarin, and pre-rRNAs to UBF-associated NORs generates segregated mininucleoli that are similar to the larger ones observed in interphase cells grown under the same conditions. Pre-rRNAs are juxtaposed to UBF-nucleolin-fibrillarin caps that may represent the segregated nucleoli observed by electron microscopy. These findings lead to a revised model of nucleologenesis. We propose that nucleolar formation at the end of mitosis results from direct recruitment of processing factors and pre-rRNAs to UBF-associated NORs before or at the onset of rDNA transcription. This is followed by fusion of prepackaged prenucleolar bodies into the nucleolus. Pre-ribosomal ribonucleoproteins synthesized in the previous cell cycle may contribute to postmitotic nucleologenesis. INTRODUCTIONThe nucleus is a complex structure within which various functions and components are spatially and temporally organized and interregulated (reviewed by Lamond and Earnshaw, 1998;Dreyfuss and Struhl, 1999). Nucleoli represent the most prominent example of this organization. The major function of the nucleolus is ribosome biogenesis (reviewed by Busch and Smetana, 1970). rRNAs are synthesized, processed, cleaved, and assembled with ribosomal proteins in the nucleolus before export to the cytoplasm. The nucleolus is composed of three structurally distinguishable constituents: fibrillar centers, dense fibrillar components, and granular components, as observed by electron microscopy (reviewed by Busch and Smetana, 1970;Hadjiolov, 1985). Although the spatial and temporal relationship between rRNA synthesis and the three structural constituents remains to be clarified, it is generally thought that transcription of rDNA takes place in a transient area between the fibrillar centers and the dense fibrillar components and that rRNA processing and preribosomal particle assembly progress from the dense fibrillar components to the surrounding granular components (reviewed by Spector et al., 1993;Shaw and Jordan, 1995;Scheer and Hock, 1999). More recent evidence (reviewed by Pederson, 1998;Garcia and Pillus, 1999) suggests that nucleoli have additional functions related to the cell cycle Visintin et al., 1999), cellular aging (Straight et al., 1999), signal recognition particle biosynthesis (Jacobson and Pederson, 1998),...

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Section: Pre-rrna Processing Factors Are Directly Recruited To Activementioning

confidence: 91%

mentioning

confidence: 98%

Initiation of Nucleolar Assembly Is Independent of RNA Polymerase I Transcription

Dousset

Wang

Verheggen

et al. 2000

MBoC

124

122

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“…6H2O (6), and separated into nuclei and cytoplasm. Detergent-rinsed nuclei (7) were lysed in HSB containing DNase, 100 ,ug/ml, and separated into nucleolar and nucleoplasmic fractions by zonal centrifugation in sucrose gradients (8) . RNA was released from the pellet of nucleoli by resuspension in NETS buffer and was recovered from the supernatant nucleoplasmic fraction by precipitation with 2 .5 volumes of 95% ethanol (1 hr at -20°C), after which the RNA was collected by centrifugation (10 min at 3000 rpm, International model PR-2, Inter- …”

Section: Cell Fractionation and Rna Extractionmentioning

confidence: 99%

Rna Synthesis in Hela Cells

Pederson

Robbins

1970

The Journal of Cell Biology

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Interphase HeLa cells manifest a stepwise shutoff of RNA synthesis when the tonicity of the extracellular medium is gradually increased . Synthesis of heterogeneous nuclear RNA is most sensitive and is selectively inhibited at 1 .5 times isotonicity (450 milliosmols/liter), while 45S ribosomal RNA synthesis is not affected significantly below 2 .0 times isotonicity . Transfer RNA synthesis is least sensitive to increased osmolarity and is not completely inhibited until the electrolyte concentration of the medium is elevated to 2 .8 times isotonicity. Although the transcription and methylation of 45S ribosomal precursor is unaffected at 1 .5 times isotonicity, there is pronounced impairment of its processing into 32S and 18S RNA. Using a refined cell synchronization technique, we have been able to compare these effects of hypertonicity with the shutoff of RNA synthesis which occurs during the G2 -prophase interval of the cell division cycle . In this case, as with random cells in hypertonic medium, a selective inhibition of heterogeneous nuclear RNA synthesis and slowed processing of 45S ribosomal RNA were found, whereas synthesis of 45S and transfer RNA continued unabated throughout G 2-prophase. While it is known that RNA synthesis essentially ceases during metaphase, we have noted that transfer RNA synthesis continues in metaphase at 10-15% of the interphase rate, which is of particular interest in view of the relative resistance of this species to hypertonicity . The close correlation between the patterns of cessation of RNA synthesis at mitosis and during exposure to hypertonic medium supports our earlier contention that alteration of intracellular electrolyte levels provides a useful model for studying the mechanism of mitosis .

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“…Informosomes could be characterized in cell nuclei [3][4][5][6] and in the cytoplasm [7][8][9][10][11]. Due to the scarcity of ribosomal-like particles in nuclei, nuclear informosomes could be isolated in a rather pure form [3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Isolation of cytoplasmic non‐ribosomal ribonucleoprotein particles (informosomes)

et al. 1972

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Localization and kinetics of formation of nuclear heterodisperse RNA, cytoplasmic heterodisperse RNA and polyribosome-associated messenger RNA in HeLa cells

Cited by 576 publications

References 19 publications

Initiation of Nucleolar Assembly Is Independent of RNA Polymerase I Transcription

Initiation of Nucleolar Assembly Is Independent of RNA Polymerase I Transcription

Rna Synthesis in Hela Cells

Isolation of cytoplasmic non‐ribosomal ribonucleoprotein particles (informosomes)

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