scholarly journals Rat liver nuclear skeleton and small molecular weight RNA species.

1978 ◽  
Vol 76 (3) ◽  
pp. 692-704 ◽  
Author(s):  
T E Miller ◽  
C Y Huang ◽  
A O Pogo
Keyword(s):  
Molecular Weight ◽  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Rat Liver ◽  
Protein Matrix ◽  
Small Molecular Weight ◽  
Rat Liver Nuclei ◽  
Nuclear Rna ◽  
Liver Nuclei ◽  
Preceding Communication

Small molecular weight RNA species (smwRNAs) were studied in rat liver nuclei with and without chromatin as well as with and without nuclear envelope and nucleoplasm. From all the species identified, only two, N5 and 5Sb, were related to ribosomes. The others were localized exclusively in the nuclear skeleton or the spongelike network that was described in the preceding communication. This network or protein matrix contains a less abundant but exclusive set of molecules designated 5Sa, N1, and 4.5S, as well as other more abundant molecules which also exist in rat liver endoplasmic reticulum but not in polysomes or postribosomal RNP complexes. The smwRNAs behave like HnRNA; they remain located in the nuclear skeleton when nuclei are deprived of nucleoplasm and chromatin. With the information presently available, it is not possible to know whetherer both species are in the same or different RNP complexes and whether some of the smwRNAs contribute to the architecture of the nuclear skeleton. Distinct from any other nuclear RNA species, smwRNAs have two unique properties: facility of extraction, and resistance to nuclear ribonuclease digestion.

scholarly journals Cytochemical studies on the relation of nucleoside triphosphatase activity to ribonucleoproteins in isolated rat liver nuclei.

1980 ◽  
Vol 28 (1) ◽  
pp. 27-35 ◽  
Author(s):  
A Vorbrodt ◽  
G G Maul
Keyword(s):  
Nuclear Envelope ◽  
Rat Liver ◽  
Enzyme Reaction ◽  
Point Of View ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Isolated Rat Liver ◽  
Rat Liver Nuclei ◽  
Liver Nuclei ◽  
Isolated Rat

Cytochemical tests for nucleosidetriphosphatase (NTPase) and Bernhard's preferential staining for ribonucleoproteins (RNP) were applied to isolated rat liver nuclei. The strongest and most easily reproducible positive reaction for NTPase was detected at pH 7.7 with ATP and GTP. This reaction was activated by Mg2+ and Ca2+ and inhibited by Be2+, Zn2+, quercetin, and ribonuclease. The major sites of enzyme reaction were intranuclear RNA-containing structures. Incubation of nuclei in ATP-stimulated RNA-release medium eliminated a considerable part of the material showing both NTPase reaction and staining for RNP; the perichromatin granules disappeared, while interchromatin granules remained. NTPase activity in the nuclear envelope seems to be associated with the annular part of nuclear pore complexes (permanent component) and with RNP particles translocated through nuclear pores or attached to the surface of nuclei (transitional component). From a morphological point of view, these observations support previous biochemical data suggesting the existence of a connection between NTPase activity and the translocation of RNP particles through the nuclear envelope.

scholarly journals cAMP-dependent protein kinase phosphorylates and activates nuclear Ca2+-ATPase

1998 ◽  
Vol 95 (16) ◽  
pp. 9178-9183 ◽  
Author(s):  
Patrick J. Rogue ◽  
Jean-Paul Humbert ◽  
Alphonse Meyer ◽  
Solange Freyermuth ◽  
Marie-Marthe Krady ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Nuclear Envelope ◽  
Rat Liver ◽  
Protein Band ◽  
Partial Purification ◽  
Dependent Protein Kinase ◽  
Rat Liver Nuclei ◽  
Camp Dependent Protein Kinase ◽  
Dependent Protein ◽  
Liver Nuclei

A Ca2+-pump ATPase, similar to that in the endoplasmic reticulum, has been located on the outer membrane of rat liver nuclei. The effect of cAMP-dependent protein kinase (PKA) on nuclear Ca2+-ATPase (NCA) was studied by using purified rat liver nuclei. Treatment of isolated nuclei with the catalytic unit of PKA resulted in the phosphorylation of a 105-kDa band that was recognized by antibodies specific for sarcoplasmic reticulum Ca2+-ATPase type 2b. Partial purification and immunoblotting confirmed that the 105-kDa protein band phosphorylated by PKA is NCA. The stoichiometry of phosphorylation was 0.76 mol of phosphate incorporated/mol of partially purified enzyme. Measurement of ATP-dependent 45Ca2+ uptake into purified nuclei showed that PKA phosphorylation enhanced the Ca2+-pumping activity of NCA. We show that PKA phosphorylation of Ca2+-ATPase enhances the transport of 10-kDa fluorescent-labeled dextrans across the nuclear envelope. The findings reported in this paper are consistent with the notion that the crosstalk between the cAMP/PKA- and Ca2+-dependent signaling pathways identified at the cytoplasmic level extends to the nucleus. Furthermore, these data support a function for crosstalk in the regulation of calcium-dependent transport across the nuclear envelope.

scholarly journals Nuclear-envelope vesicles as a model system to study nucleocytoplasmic transport. Specific uptake of nuclear proteins

1987 ◽  
Vol 241 (1) ◽  
pp. 213-219 ◽  
Author(s):  
N Riedel ◽  
H Fasold
Keyword(s):  
Nuclear Envelope ◽  
Rat Liver ◽  
Protein Translocation ◽  
High Mobility ◽  
Preceding Paper ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Proteins ◽  
Rat Liver Nuclei ◽  
Liver Nuclei

In the preceding paper [Riedel & Fasold (1987) Biochem. J. 241, 203-212] we have described a procedure for the preparation of nuclear-envelope vesicles (NE vesicles) from rat liver nuclei. These vesicles, which are largely free of components of the nuclear interior, were employed in an assay system in vitro to study protein translocation across the NE. We found that nuclear proteins such as histones, high-mobility-group proteins and acidic chromosomal proteins are specifically taken up and accumulated in the NE vesicles, whereas there is little or no affinity for non-nuclear proteins like immunoglobulin, myoglobin and cytochrome c. The kinetics of histone uptake into the NE vesicles are similar to those obtained for whole rat liver nuclei, and comparative studies with non-vesicular NEs prepared by deoxyribonuclease I-treatment (DNAase-NEs) indicate that the NE of the vesicles affects the uptake kinetics and increases the capacity for nuclear proteins. The uptake of histones into NE vesicles, but not the binding to DNAase-NEs, can be stimulated by GTP and GDP. Furthermore, we found that even very large molecules can be entrapped in the vesicles during their preparation. These results indicate that the NE vesicles might provide a useful system in vitro with which to investigate the structures and mechanisms involved in protein translocation across the NE.

scholarly journals Phosphoinositide signalling enzymes in rat liver nuclei: phosphoinositidase C isoform β1 is specifically, but not predominantly, located in the nucleus

1993 ◽  
Vol 289 (3) ◽  
pp. 617-620 ◽  
Author(s):  
N Divecha ◽  
S G Rhee ◽  
A J Letcher ◽  
R F Irvine
Keyword(s):  
Nuclear Envelope ◽  
Rat Liver ◽  
Rat Liver Nuclei ◽  
Liver Nuclei ◽  
G Alpha Q ◽  
Triton X ◽  
Total Beta

The presence of phosphoinositide-mobilizing enzymes has been investigated in purified rat liver nuclei by radiolabelling and by probing with antibodies. A Ca(2+)-activated phosphoinositidase C (PIC) is present and was shown immunologically to be the beta 1 isoform. No gamma- or delta-PIC was found. However, only 5% of the total beta 1-PIC isoform is nuclear, with the majority being cytosolic. G alpha q and G alpha 11, the suggested physiological activators of beta 1-PIC, were not present. A PtdIns4P 5-kinase is also present, which immunologically is shown to be the C isoform. All of these nuclear inositide enzymes still remained after the removal of the nuclear envelope with Triton X-100, consistent with the concept of an intranuclear inositide cycle [Divecha, Banfic and Irvine (1991) EMBO. J. 10, 3207-3214].

scholarly journals Preparation and characterization of nuclear-envelope vesicles from rat liver nuclei

1987 ◽  
Vol 241 (1) ◽  
pp. 203-212 ◽  
Author(s):  
N Riedel ◽  
H Fasold
Keyword(s):  
Nuclear Envelope ◽  
Rat Liver ◽  
Nucleocytoplasmic Transport ◽  
Transport Processes ◽  
High Yield ◽  
Complex Nature ◽  
Rat Liver Nuclei ◽  
Deoxyribonuclease I ◽  
Transport Studies ◽  
Liver Nuclei

We describe a procedure for the preparation of sealed nuclear-envelope vesicles from rat liver nuclei. These vesicles are strikingly similar in their polypeptide composition when compared with those of nuclear envelopes prepared conventionally using deoxyribonuclease I. Subfractionation analysis by means of extraction with high salt and urea show that the components of the nuclear envelope, e.g. the pore-complex/lamina fraction, are present. The residual DNA content is only 1.5%, and typical preparations consist of about 80% vesicles, with the vesicular character of these envelopes shown by microscopic and biochemical studies. The vesicles can be obtained in high yield, are tight and stable for at least two days and are enriched in a nucleoside triphosphatase thought to be involved in nucleocytoplasmic transport processes. Because the vesicles are largely free of components of the nuclear interior, but retain properties of intact nuclei, we believe that they are a valuable model system to study nucleocytoplasmic transport. Although in transport studies with isolated nuclei interference from intranuclear events has to be considered, the nuclear-envelope vesicles provide the possibility of studying translocation alone. Furthermore, the less complex nature of these vesicles compared with whole nuclei should facilitate investigation of the components involved in the regulation of nuclear transport processes.

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