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At least 145 records · Page 8Linked to original sources
PubMed1977

Metrizamide dissociates nuclear particles containing heterogeneous nuclear RNA.

Metrizamide gradients were tested for the possible fractionation of the constitutive units of nuclear particles. Material from 35-55 S monoparticles was indeed distributed along the gradient but rerun experiments, CsCl density determinations, formaldehyde fixation prior to centrifugation suggested that the separation was due to dissociation or (and) action of endogeneous ribonucleases rather than to monoparticle fractionation. That dissociation had indeed occured was confirmed by the study of 60-110 S polyparticles. They were dissociated into ribonucleoproteins rich in phosphoproteins and into free proteins. These products were essentially similar to those obtained after NaCl treatment of the particles though the modes of action of metrizamide and NaCl are likely to be different. The loss of proteins from particles reaches 60-70% and we conclude that metrizamide gradients are not utilizable for the fractionation of the units of nuclear particles.

Animals↗
PubMed1977

The 5'-termini of heterogeneous nuclear RNA: a comparison among molecules of different sizes and ages.

The composition of the 5' polyphosphorylated and capped termini of pulse labeled hnRNA from mouse L cells was analyzed by two-dimensional electrophoresis. Purine tri- and diphosphates: pppG, pppA, ppG and ppA; as well as four varieties of cap structure: m7GpppXm, Xm = Gm, (m6) Am, Cm and Um, were detected. With increasing labeling time the relative proportion of hnRNA molecules with tri- and diphosphorylated 5' ends decreases and the relative proportion of capped hnRNA increases, indicating that caps are metabolically more stable than the polyphosphate termini. About half of the hnRNA molecules that are labeled within 2 hr have capped ends. This finding, together with results of earlier kinetic and structural studies, implies that a relatively high proportion of the labeled hnRNA molecules are mRNA precursors. Large hnRNA molecules exhibit a higher proportion of capped ends and a lower proportion of 5'-triphosphate ends as compared to small hnRNA. Given the lower stability of triphosphate termini relative to caps, this result may mean that capping of some hnRNA molecules can occur before the completion of transcription.

Base Sequence↗
PubMed1975

Heterogeneous nuclear rna from lymphocytes of chronic lymphocytic leukaemia: adenylate-rich and double-stranded regions.

Rapidly labelled high molecular weight nuclear RNA from lymphocytes of chronic lymphocytic leukaemia was analysed for ribonuclease-stable adenylate-rich and double-stranded regions. The polyadenylate content corresponds to 0.4-0.5 percent and the content of double-stranded sequences to 2-4 percent of the total nucleotides. Partial association of polyadenylate segments with double-stranded regions was found by comparative analysis of (3H)-adenosine and (3H)-uridine labelled ribonuclease-stable RNA before and after thermal denaturation. Comparison with normal lymphocytes shows lower proportions of polyadenylate-containing RNA binding to poly(U)-Sepharose in leukaemia cells than in normals. Partial degradation of rapidly labelled high molecular weight RNA was found in leukaemia cases with low white cell counts.

Adenosine↗
PubMedDate not supplied

[DNA synthesis on the heterogeneous nuclear RNA template catalysed by DNA polymerase of avian myeloblastosis virus].

Template activity of nuclear pre-mRNA has been investigated in DNA-polymerase reaction. Active synthesis of DNA was demonstrated on pre-mRNA as a template in the absence of primer. A part of synthetic activity may be attributed to the traces of DNA present in the pre-mRNA preparation. Addition of oligo(dT)10 to the template stimulated the synthesis of DNA product due to transcription of heteropolymeric regions near the poly(A). The rate of DNA synthesis was different depending on the fraction of template used: the RNA extracted by hot phenol at 85 degrees showed higher template activity without adding of primer than the 65 degrees C fraction. On the contrary 65 degrees C pre-mRNA which is known to contain greater quantity of molecules with poly(A) at the 3'-end is more strongly stimulated by addition of oligo(dT). The nuclear RNA corresponding to the precursors of rRNAs extracted at 40 degrees C were not transcribed by the reverse transcriptase. The size of the DNA-product (about 7-8S in alkaline sucrose gradient) did not depend on the size of the template neither on the presence of oligo(dT)10 primer. The inhibition of the second DNA strand synthesis with actinomycin D had also no influence on the size of DNA-product.

Avian Leukosis Virus↗
PubMed1971

Transcription of the polyoma virus genome: synthesis and cleavage of giant late polyoma-specific RNA.

The size of virus-specific RNA synthesized in cultured mouse kidney cells infected with polyoma virus was estimated by electrophoresis and sedimentation analysis of RNA extracts from whole cells. Newly synthesized "late" polyoma-specific RNA appears as "giant" molecules of heterogeneous size, up to several times larger than a strand of polyoma DNA (1.5 x 10(6) daltons). Treatment with dimethylsulfoxide or urea showed that the large size of these molecules is not due to aggregation. Giant polyoma-specific RNA is strikingly similar in size distribution to "nuclear messenger-like" RNA ("heterogeneous nuclear" RNA) of the host cell. Subsequent to its synthesis, some of the giant polyoma-specific RNA appears to be cleaved to at least three smaller species.

Animals↗
PubMed1978

Complex population of mRNA sequences in large polyadenylylated nuclear RNA molecules.

Polyadenylylated heterogeneous nuclear RNA [poly(A)-hnRNA] from mouse brain was subjected to electrophoresis in agarose gels containing CH3HgOH, and molecules larger than 8 kilobases or 13 kilobases were recovered. cDNA was then transcribed from polyadenylylated RNA fragments cleaved from these large molecules. The resulting cDNA hybridized almost to completion with poly(A)-mRNA isolated from mouse brain polysomes. From the hybridization kinetics of this cDNA with its template RNA, it was estimated that the sequence complexity of the 3'-proximal sequences (of the same average size as mRNA) of the greater than 8 kilobase poly(A)-hnRNA was about 57,000 kilobases. The sequence complexity of poly(A)-mRNA, estimated from the template-driven hybridization kinetics of its respective cDNA, was about 110,000 kilobases. It is concluded that most, if not all, of the 3'-proximal sequences of large poly(A)-hnRNA molecules are homologous with mRNA in the mouse brain and that at least 40,000 different mRNA sequences (or portions of mRNA sequences) are represented in the 3'-proximal sequences of greater than 8 kilobase poly(A)-hnRNA.

Animals↗
PubMed1985

Specific regions of the intervening sequences of beta-globin RNA are resistant to nuclease in 50S heterogeneous nuclear RNA-protein complexes.

The specific assembly of heterogeneous nuclear RNA-protein complexes (hnRNPs) containing precursor beta-globin RNA was investigated by using the 50S hnRNP released from chicken reticulocyte nuclei by endogenous nuclease. The nuclease-resistant regions were mapped on adult beta-globin intervening sequences (IVS) at the resolution of nucleotides with an RNA mapping method [Patton, J. R. and Chae, C.-B. (1983) J. Biol. Chem. 258, 3991-3995]. We found that there is one 28-nucleotide-long nuclease-resistant region in the first IVS and there are four nuclease-resistant regions in the second IVS. Of particular interest is the presence in 50S hnRNP of a nuclease-resistant region (24-28 nucleotides long) in both IVS immediately upstream from the putative lariat branch site in an RNA splicing intermediate. Our results demonstrate that hnRNPs containing precursor beta-globin RNA are, like those containing mature beta-globin RNA, assembled in a site-specific manner.

Animals↗
PubMed1984

Effects of dimethylnitrosamine on RNA synthesis and metabolism in mouse liver.

Following i.p. injection of dimethylnitrosamine into male C57BL mice, synthesis of liver nuclear heterogeneous RNA was inhibited significantly, reaching approximately 20% of control within 2 hr of a dose of 40 mg/kg. Synthesis of nucleolar RNA was also inhibited, although to a smaller extent, reaching about 70% of control after the same treatment. These effects were observed both during RNA synthesis in vivo and during in vitro transcription with isolated nuclei and nucleoli. Examination of RNA polymerases I and II, isolated and partially purified by diethylaminoethyl Sephadex column chromatography, did not indicate any change either in their activities in the transcription of exogenous DNA or in their in vivo binding to chromatin. On the other hand, the activity of purified chromatin as a template for transcription by added, partially purified RNA polymerase II was significantly reduced, suggesting that carcinogen-induced damage to chromatin was the cause of the observed inhibition of heterogeneous RNA synthesis. When purified DNA was used in place of chromatin as a template for transcription by partially purified RNA polymerase II, no inhibition was observed. Dimethylnitrosamine treatment had a pronounced effect on the kinetics of appearance of the cytoplasmic RNA species. Four hr after a 40-mg/kg dose of dimethylnitrosamine, the rate of appearance in the cytoplasm of polyadenylate-containing RNA was inhibited by 50%, while that of 4S, 18S, and 28S ribosomal RNA was inhibited by over 80%.

Animals↗
PubMed1996

Transcriptional regulation of insulin-like growth factor-binding protein-5 by prostaglandin E2 in osteoblast cells.

Insulin-like growth factor (IGF)-binding protein-5 (IGFBP-5) is an autocrine and paracrine factor that modulates the effects of IGFs. We examined the mechanisms that regulate IGFBP-5 synthesis by PGE2 in osteoblast-enriched cells from fetal rat calvaria (Ob cells). PGE2 at 1 microM for 2-8 h increased IGFBP-5 heterogeneous nuclear RNA levels and did not change the half-life of IGFBP-5 messenger RNA in Ob cells, suggesting that PGE2 stimulates IGFBP-5 transcription. To analyze the elements responsible for this effect, regions of the mouse IGFBP-5 promoter from -2695 to +120 bp were ligated into pGL-2-basic and transiently transfected into Ob cells. PGE2 caused a time- and dose-dependent increase in IGFBP-5 promoter activity. Further analysis revealed two potential PGE2-responsive regions in the -2695 to -1470 and the -989 to -332 fragments. The effect of PGE2 on IGFBP-5 messenger RNA and heterogeneous nuclear RNA levels was mimicked by forskolin and inhibited by the PKA inhibitor H-89, suggesting that part of the PGE2 effect was mediated through a cAMP-dependent pathway. H-89 also blocked basal and PGE2-stimulated IGFBP-5 promoter activities. We conclude that PGE2 regulates IGFBP-5 synthesis in Ob cells by transcriptional mechanisms. PKA-dependent pathways account for part of the effect of PGE2 on IGFBP-5 expression. Deletion analysis of the IGFBP-5 promoter suggests the presence of two PGE2-responsive regions.

Animals↗