Transcriptional Activity Of Nuclei Research Articles

Transcriptional activity of nuclei in 2-cell blocked mouse embryos

Embryos of inbred mouse strains stop their cleavage at the late 2-cell stage and this phenomenon is known as the “2-cell block in vitro”. In the present work we used microinjections of 5-bromouridine 5′-triphosphate (BrUTP) to examine the transcriptional status of blocked embryos. We also traced nuclear distribution of hyperphosphorylated form of RNA polymerase II in such embryos. We found that transcriptional activity is gradually decreased when the embryos stay in block. This is accompanied by prominent increasing of the size of SC35 nuclear speckles that begin to accumulate hyperphosphorylated RNA polymerase II.

Transcriptional activity of nuclei in multinucleated osteoclasts and its modulation by calcitonin.

The function of osteoclasts is to digest the calcified bone matrix. Osteoclasts, together with myotubes, are among the rare examples of multinucleated cells found in higher vertebrates, resulting from the fusion of mononucleated progenitors belonging to the monocyte/macrophage lineage. So far, no information is available about function and transcriptional activity of multiple nuclei in osteoclasts. We have used a run-on technique to visualize RNA synthesis in individual nucleus. We provide the first evidence that nuclei of resorbing osteoclasts, isolated from chick embryo long bones, or differentiated in vitro from murine spleen cells in presence of RANKL and macrophage-colony stimulating factor, are all transcriptionally active. Nevertheless, if transcriptional activity is the same for all the nuclei within a cell, its level varies between osteoclasts: osteoclasts with highly active nuclei are always associated with resorption pits. We found that global transcription activity of resorbing osteoclasts seeded on calcified matrix is down-regulated after 5-h treatment with calcitonin, which transiently blocks resorption. This effect is reversible because calcitonin removal led to nuclear transcription activation. These results indicate a strong correlation between transcription and resorption. Finally, our data indicate that the resorption pit surface is linearly related to the nuclei number per osteoclast, strongly suggesting that functional advantage of osteoclast multinucleation is to improve resorption efficiency.

Transcriptional Activity of Nuclei in Multinucleated Osteoclasts and Its Modulation by Calcitonin

Transcriptional Activity of Nuclei in Multinucleated Osteoclasts and Its Modulation by Calcitonin

Protein kinase C-mediated down-regulation of beta(2)-adrenergic receptor and gene expression in rat C6 glioma cells.

We investigated the regulation of beta(2)-adrenergic receptors (beta(2)AR) by protein kinase C (PKC) in rat C6 glioma cells at the levels of receptor activity, protein expression and gene expression. Cells exposed to 4beta-phorbol-12-myristate-13-acetate (PMA), a potent activator of PKC, exhibited a time- and concentration-dependent decrease in beta(2)AR binding activity. Maximum down-regulation was approximately 50% by 24 h and western blot analysis revealed a parallel decrease in beta(2)AR protein. In addition, PMA treatment resulted in an acute desensitization of beta(2)AR-stimulated cyclic AMP response prior to any reduction in receptor levels. PMA exposure also affected steady-state beta(2)AR mRNA levels in a time-dependent, biphasic manner. During the first 4 h, levels decreased by approximately 60% and then slowly recovered to approximately 75% of control by 24 h. As the reduction in receptor mRNA was not due to a decrease in its stability, we examined beta(2)AR gene transcription by nuclear run-on assays. Transcriptional activity in nuclei from C6 cells treated with PMA for 2 h was reduced by 70% compared to controls. Thus PKC can regulate beta(2)AR at least two levels: the first being an acute desensitization of receptor function, and the second being a more prolonged repression of receptor gene transcription that in turn results in decreased receptor expression.

Induction of hepatic ATP-citrate lyase by insulin in diabetic rat--effects of insulin on the contents of enzyme and its mRNA in cytosol, and the transcriptional activity in nuclei.

The effects of insulin on ATP-citrate lyase, its mRNA in cytosol, and the transcriptional activity in nuclei of diabetic rat liver were studied. Experimental diabetes was induced by an intraperitoneal injection of streptozotocin, and livers were removed from rats at 0, 1, 3, 6, 16, and 72 hours after the administration of insulin. ATP-citrate lyase began to increase at 16 hours, and continuously increased until 72 hours. The amount of mRNA encoding ATP-citrate lyase increased abruptly at 16 hours, then decreased to near basal level in 72 hours. No change in the transcription rate was observed until 3 hours after insulin administration. However, the activity increased 4-fold at 6 hours and 7-fold at 16 hours, 16-fold at 6 hours and 28-fold at 16 hours when pGACL1 and pGACL2 were used as probes, respectively, preceding the increase in the amounts of mRNA and the enzyme. It is suggested that the increase in the amount of ATP-citrate lyase by insulin is primarily due to the increase in the transcriptional activity of the gene in nuclei, which results in the subsequent increase in the amount of mRNA for the biosynthesis of ATP-citrate lyase in cytosol.

A Model for Motor Endplate Morphogenesis: Diffusible Morphogens, Transmembrane Signaling, and Compartmentalized Gene Expression

A mathematical model for the formation and maintenance of synaptic contacts at the motor endplate is proposed. It is based on diffusion between sarcoplasmic nuclei of limiting amounts of a morphogen substance. The morphogen is postulated to act on genetic switch-like intranuclear units and to regulate positively both the transcription of its own gene and that of acetylcholine receptor (AChR) subunit genes. The efficacy of autoregulation is assumed to be depressed by electrical activity; while AChR genes transcription is enhanced by anterograde neural factors. Thus the model involves Turing's classical ingredients: autocatalysis and short range activation by the morphogen, and long range inhibition by electrical activity. Our predictions include: the stabilization of a single, transcriptionally active nucleus located in the central region of the developing muscle fiber (or myotube); the frequent occurrence of transcriptional activity in nuclei at the tendinous ends; and the onset, upon denervation of adult muscle, of transcription waves, starting from both the central site and the tendinous nuclei. In noninnervated fibers, the calculations show that spontaneous, irregular electrical activity leads to a variety of near-periodic spatial patterns of transcription; these are also predicted in innervated fibers when the depressing effect of electrical activity is weak, giving rise to the stabilization of multiple endplates as occurs in muscles with distributed innervation.

Role of Cytokinins in Development and Metabolism of Barley Leaves. VII. Effect of Light and Kinetin on the Transcriptional Activity of Nuclei from Etiolated Leaves

Summary Leaves excised from etiolated seedlings of Hordeum vulgare L. cv. Triumph were exposed to light for 6 h in the presence or absence of kinetin at 5 µM. Nuclei were isolated and their activity in [ 14 C]-UTP incorporation into an acid insoluble product was determined. This activity increased after exposition of leaves to light (in comparison with the zero-time dark control) due to transcription catalyzed by both RNA polymerases I and II. The response to kinetin depended on the physiological age of leaves. In younger (usually 8-day-old) leaves, kinetin promoted the rate of transcription mainly connected with RNA polymerase I. In somewhat older (about 10-d-old) leaves, kinetin inhibited the transcription, mainly at the expense of activity connected with RNA polymerase II.

Transcriptional activity of nuclei from WI-38 cells at various passages.

Transcriptional activity of nuclei from human diploid fibroblast (WI-38) cells at different passage levels was studied with endogenous RNA polymerase. The rate and extent of the RNA synthesis decreased when the nuclei were prepared from senescent cells. The decreased activity of RNA synthesis in senescent cell nuclei was demonstrated from both the transcriptional assay and the estimation of the processing activity, i.e., polyadenylation of the transcripts.

Induction of cleft palates: effects of triamcinolone acetonide on transcription in isolated nuclei.

The effect of triamcinolone acetonide on the transcriptional activity in nuclei isolated from maternal A/J mouse livers and embryonic maxillary processes (EMP) has been studied. Triamcinolone acetonide (TAC, 13 mg/kg body weight) was administered to A/J mice on day 12.5 of gestation, and the mice were sacrificed at different time periods following injection. We find a significant increase in transcription in liver nuclei, and a decrease in this activity in nuclei from embryonic maxillary processes in response to TAC at 16 to 20 hours following injection. With the drug alpha-amanitin we show that the effect of TAC on transcription in EMP cannot be due to fluctuations in the concentration of endogenous RNA polymerase B. This is further substantiated by studies on the transcription of EMP-nuclei in the presence of exogenous DNA template. Relative to controls, the data demonstrates that the concentrations of RNA polymerases A and B in EMP-nuclei remain unchanged in response to TAC. Conversely, stimulated liver nuclei result in significant increases in the concentrations of RNA polymerases A and B. We therefore propose that in embryonic maxillary processes TAC induces changes in the chromatin template which may interfere with normal development.