Nuclear 30 S RNP Particles

Samarina, O. P.; Krichevskaya, A. A.

doi:10.1016/b978-0-12-147609-0.50007-1

Cited by 13 publications

(14 citation statements)

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“…This event is followed by loop excision (15). These findings and others reviewed elsewhere (16)(17)(18) continue to indicate that monoparticles may function in the events of hnRNA processing.…”

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confidence: 92%

General organization of protein in HeLa 40S nuclear ribonucleoprotein particles.

Lothstein

Arenstorf

Chung

et al. 1985

The Journal of Cell Biology

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The majority of the protein mass of HeLa 40S heterogeneous nuclear ribonucleoprotein monoparticles is composed of multiple copies of six proteins that resolve in SDS gels as three groups of doublet bands (A1, A2; B1, B2; and C1, C2) (13eyer, A. L., M. E. Christensen, 13. W. Walker, and W. M. LeStourgeon. 1977. Cell. 11: 127-138). We report here that when 40S monoparticles are exposed briefly to ribonuclease, proteins A1, C1, and C2 are solubilized coincidentally with the loss of most premessenger RNA sequences. The remaining proteins exist as tetramers of (A2)3(B1) or pentamers of (A2)3(B1)(132). The tetramers may reassociate in highly specific ways to form either of two different structures. In 0.1 M salt approximately 12 tetramers (derived from three or four monoparticles) reassemble to form highly regular structures, which may possess dodecahedral symmetry. These structures sediment at 43S, are 20-22 nm in width, and have a mass near 2.3 million. These structures possess 450-500 bases of slowly labeled RNA, which migrates in gels as fragments 200-220 bases in length. In 9 mM salt the tetramers reassociate to form 2.0 M salt-insoluble helical filaments of indeterminant length with a pitch near 60 nm and diameter near 18 nm. If 40S monoparticles are treated briefly with nuclease-free proteases, the same proteins solubilized by nuclease (A1, C1, and C2) are preferentially cleaved. This protein cleavage is associated with the dissociation of most of the heterogeneous nuclear RNA. Proteins A2 and B1 again reassemble to form uniform, globular particles, but these sediment slightly slower than intact monoparticles. These findings indicate that proteins A1, C1, and C2 and most of the premessenger sequences occupy a peripheral position in intact monoparticles and that their homotypic and heterotypic associations are dependent on protein-RNA interactions. Protein cross-linking studies demonstrate that trimers of A1, A2, and C1 exist as the most easily stabilized homotypic association in 40S particles. This supports the 3:1 ratio (via densitometry) of the A and C proteins to the B proteins and indicates that 40S monoparticles are composed of three or four repeating units, each containing 3(A1),3(A2),1(B1),1(B2),3(C1), and 1 (C2).When isolated nuclei from mammalian cells are disrupted briefly with ultrasound (1-3) or extracted with low ionic strength buffers (4, 5), the majority of the premessenger RNA sequences (heterogeneous nuclear [hn] RNA) ~ are recovered Abbreviations used in this paper. CuP, (orthophenanthrolinehCu(II) complex; DTBP, 3,3'-dimethyl dithiobispropionimidate dihydrochloride; hnRNA, heterogeneous nuclear RNA; hnRNP, heteroge-1570 in 20-25-nm 40S ribonucleoprotein complexes or monoparticles (1-13). Along with hnRNA, these monoparticles are primarily composed of multiple copies of six nucleus-specific polypeptides that migrate in SDS polyacrylamide gels as three groups of doublet bands (A1,A2; B1,B2, and C1,C2) with neous nuclear ribonucleoprotein; NRS, nuclease-resistant structure; OD, optical ...

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confidence: 92%

General organization of protein in HeLa 40S nuclear ribonucleoprotein particles.

Lothstein

Arenstorf

Chung

et al. 1985

The Journal of Cell Biology

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“…Under conditions of minimal nuclease activity, 70 to 95% of this RNA is recovered in large ribonucleoprotein (RNP) complexes which sediment from 30S to more than 200S (26, 39, 52). Electron micrographs of the faster-sedimenting complexes reveal 20-to 25-nm particles arranged either as an array of polyparticles (29,36,42,43,52,53,61) or as clusters of particles when nuclease activity is aggressively inhibited (56). Upon mild nuclease activity the polyparticle complexes are lost and the cleaved RNA (mostly 500-to 1,000-nucleotide [nt] fragments) is recovered in 20-to 25-nm 30S-40S monoparticles (heterogeneous nuclear RNP [hnRNP] particles or ribonucleosomes) (3, 10, 18, 56, 64).…”

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confidence: 99%

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confidence: 99%

The C-protein tetramer binds 230 to 240 nucleotides of pre-mRNA and nucleates the assembly of 40S heterogeneous nuclear ribonucleoprotein particles.

et al. 1994

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A series of in vitro protein-RNA binding studies using purified native (C1)3C2 and (A2)3B1 tetramers, total soluble heterogeneous nuclear ribonucleoprotein (hnRNP), and pre-mRNA molecules differing in length and sequence have revealed that a single C-protein tetramer has an RNA site size of230 to 240 nucleotides (nt). Two tetramers bind twice this RNA length, and three tetramers fold monoparticle lengths of RNA (700 nt assembly the 40S hnRNP core particle, and they provide insight into the mechanism through which the core proteins package 700-nt increments of RNA. These findings also demonstrate that unless excluded by other factors, the C proteins are likely to be located along the length of nascent transcripts.Whether released from isolated nuclei by sonic disruption or by low-salt extraction, the majority of the pre-mRNA molecules remain dispersed in solution following chromatin removal by brief centrifugation. Under conditions of minimal nuclease activity, 70 to 95% of this RNA is recovered in large ribonucleoprotein (RNP) complexes which sediment from 30S to more than 200S (26, 39, 52). Electron micrographs of the faster-sedimenting complexes reveal 20-to 25-nm particles arranged either as an array of polyparticles (29,36,42,43,52,53,61) or as clusters of particles when nuclease activity is aggressively inhibited (56). Upon mild nuclease activity the polyparticle complexes are lost and the cleaved RNA (mostly 500-to 1,000-nucleotide [nt] fragments) is recovered in 20-to 25-nm 30S-40S monoparticles (heterogeneous nuclear RNP [hnRNP] particles or ribonucleosomes) (3, 10, 18, 56, 64). Monoparticles purified from HeLa nuclei via glycerol gradients are primarily composed of six abundant nuclear proteins (the core particle proteins) (10, 28, 54, 65), which exist as three heterotypic tetramers, (A1)3B2, (A2)3B1, and (C1)3C2 (4, 7, 39). The (A2)3B1 and (C1)3C2 tetramers have been isolated and partially characterized (4, 7). The (A1)3B2 tetramer has not been isolated, but its existence is inferred from chemical cross-linking studies which reveal that Al exists in monoparticles as homotrimers (34, 41) and in a 3:1 ratio with B2. Like the histones (reviewed in reference 63), the core particle proteins are transcribed from multigene families (13,20,50) (11,17,35,38,46,65).Isolated 40S monoparticles completely dissociate upon RNA digestion with nuclease (22, 64). Spontaneous reassembly occurs in vitro upon the addition of 700 ± 20 nt of exogenous RNA or single-stranded DNA (22). Multiples of this length support the spontaneous in vitro assembly of dimers, trimers, and polyparticle complexes (22, 39). Reconstituted particles possess the same sedimentation coefficient, protein stoichiometry, chemical and UV cross-linking properties, pattern of salt-induced protein dissociation, nuclease sensitivity, and ultrastructural morphology as native hnRNP (22,27,64). Most of the noncore proteins present in initial hnRNP preparations do not quantitatively reconstitute with the core particle proteins (22, 64), a finding which indicat...

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“…These fibrils are known to contain nascent hnRNA [1] undergoing processing (see [7] for a review). Thus, these particles are possibly the counterpart of the RNP chains described by Samarina [13,24], later referred to as polyparticles (see [22] for a review). The individual granules constituting the chain probably correspond to Samarina's 30 S particles [22,24], to the 40 S particles described by Moul6 and Chauveau [17], and to 30-50 S monoparticles [13].…”

Section: Discussionmentioning

confidence: 99%

“…The study of pre-mRNAs led, from the beginning, to the finding of their structural organization in ribonucleoprorein (RNP) particles [17,23]. These particles were directly visualized by electron microscopy from material of centrifugation pellets or sucrose gradients as isolated particles [16] or polysome-like structures (reviewed in [13,22]. An interesting study comparing the morphology and some cytochemical features of perichromatin fibrils in situ and ribonucleoprotein particles isolated by biochemical methods from brain cells was carried out by Devilliers et al [4].…”

Section: Introductionmentioning

confidence: 99%

Electron microscope study of ribonucleoprotein polyparticles and their relation to perichromatin granules

Vazquez-Nin

1989

Biology of the Cell

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Nuclear ribonucleoprotein particles were studied in the central nervous system of the rat after fixation by perfusion with hypotonic-detergent formaldehyde. Beads-on-a-string structures (polyparticles or chains) formed of 14-nm granules related by a 7-nm thick filament were found. These polypartides are positively contrasted by a preferential method for ribonucleoproteins and they are sensitive to RNase. Perichromatin granules are loosened by this fixation and their internal structure is clearly depicted. They are composed of a tangled mass of 3-rim thick filaments, but lack 14-nm granules. The internal filaments of the perichromatin granules display frequent continuities with polypartides. These results show that polyparticles correspond to periehromatin fibrils visualized in nuclei by standard fixation procedures. nucleus --interphase --ribonucleoproteins --nuclear particles

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Nuclear 30 S RNP Particles

Cited by 13 publications

References 207 publications

General organization of protein in HeLa 40S nuclear ribonucleoprotein particles.

General organization of protein in HeLa 40S nuclear ribonucleoprotein particles.

The C-protein tetramer binds 230 to 240 nucleotides of pre-mRNA and nucleates the assembly of 40S heterogeneous nuclear ribonucleoprotein particles.

Electron microscope study of ribonucleoprotein polyparticles and their relation to perichromatin granules

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