Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RNA Aggregation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed1992

Yeast flocculation: reconciliation of physiological and genetic viewpoints.

Yeast flocculation results from surface expression of specific proteins (lectins). Two flocculation phenotypes were suggested by physiological and biochemical tests, whereas genetic data suggested a larger number of mechanisms of flocculation. After reviewing the biochemistry, physiology and genetics of flocculation, a new hypothesis combining the data available from these different sources, is proposed. Flocculation results when lectins present on flocculent cell walls bind to sugar residues of neighbouring cell walls. These sugar receptors are intrinsic to the mannan comprising cell walls of Saccharomyces cerevisiae. Two lectin phenotypes were revealed by sugar inhibition studies. The gluco- and mannospecific NewFlo phenotype is not, as yet, found in genetically defined strains. Mannospecific flocculation (Flo1 phenotype) is found in strains containing the genes FLO1, FLO5 and FLO8. This phenotype is also found following mutation of the TUP1 or CYC8 loci, in previously non-flocculent strains. It is therefore proposed that the structural gene for mannospecific flocculation is common or possibly ubiquitous in non-flocculent strains and in consequence, FLO1, FLO5 and FLO8 are probably regulatory genes, exerting positive control over the structural gene. Flocculation expression requires lectin secretion to the cell surface. Many of the observed 'suppressions' of flocculation may be due to mutations of the secretory process, involved in transporting structural proteins to the cell wall. The possible involvement of killer L double-stranded RNA with flocculation is suggested, given the lectin properties of viral coat proteins and an association between L double-stranded RNA and the Flo1 phenotype.

Cell Aggregation↗
PubMed1997

Construction and overexpression of a synthetic gene for human DNA methylguanine methyltransferase: renaturation and rapid purification of the protein.

A synthetic gene was constructed that encodes human DNA methylguanine methyltransferase (hMGMT). The synthetic gene was designed with a number of unique restriction sites to facilitate cassette mutagenesis and to reflect the preferences found among genes in Escherichia coli. Both the full-length gene and a gene for a functional variant (hMGMT delta C) that lacks the C-terminal 28 codons were constructed, and the genes were overexpressed using a T7 RNA polymerase promoter. The proteins are made in the form of insoluble aggregates but the truncated form of the protein (hMGMT delta C) has been successfully denatured, renatured, and purified to near homogeneity by ion exchange. Methyltransferase activity assays of hMGMT delta C demonstrate that the reconstituted protein has substantial DNA repair activity, though somewhat less than full-length hMGMT that had been expressed and purified in a soluble form. Mass spectrometry of a mixture of proteolytic fragments confirmed the protein sequence and indicated no detectable oxidation of the active site cysteine. The protein was determined to be monomeric by gel filtration chromatography, and circular dichroism spectra for renatured hMGMT delta C and fully soluble hMGMT are consistent with the renatured protein preparation being fully folded. Refolded hMGMT delta C had a curious propensity to form large aggregates in a time-dependent manner when injected into a dynamic light scattering instrument; this aggregation behavior was not observed for hMGMT purified in a soluble form. Differences in susceptibility to aggregation may account for differences in methyltransfer activity. Yields of purified protein were approximately 5 mg/liter of culture.

Amino Acid Sequence↗
PubMed2005

Differential GABAA receptor clustering determines GABA synapse plasticity in rat oxytocin neurons around parturition and the onset of lactation.

Expression, functional properties, and clustering of alpha 1-, alpha 2-, and alpha 3-subunit containing GABA(A) receptors (GABA(A)Rs) were studied in dorsomedial SON neurons of the adult female rat supraoptic nucleus (SON) around parturition. We show that, although the decay time constant (tau(decay)) of GABAergic postsynaptic currents between and within individual recordings was very diverse, ranging from fast (i.e., alpha 1-like) to significantly slower (i.e., non-alpha 1-like), there was an overall shift towards slower decaying synaptic currents during the onset of lactation. This shift is not due to changes in mRNA expression levels, because real-time quantitative PCR assays indicated that the relative contribution of alpha 1, alpha 2, and alpha 3 remained the same before and after parturition. Also, changes in phosphorylation levels are not likely to affect the tau(decay) of postsynaptic currents. In alpha-latrotoxin (alpha-LTX)-induced bursts of synaptic currents from individual synapses, the tau(decay) of consecutive synaptic events within bursts was very similar, but between bursts there were large differences in tau(decay). This suggested that different synapses within individual SON neurons contain distinct GABA(A)R subtypes. Using multilabeling confocal microscopy, we examined the distribution of postsynaptic alpha 1-, alpha 2-, and alpha 3-GABA(A)Rs, based on colocalization with gephyrin. We show that the three GABA(A)R subtypes occurred either in segregated clusters of one subtype as well as in mixed clusters of two or possibly even three receptor subtypes. After parturition, the density and proportion of clusters containing alpha 2- (or alpha 3-), but not alpha1-GABA(A)Rs, was significantly increased. Thus, the functional synaptic diversity at the postsynaptic level in dorsomedial SON neurons is correlated with a differential clustering of distinct GABA(A)R subtypes at individual synapses.

Animals↗
PubMed2005

Budesonide epimer R, LAU-8080 and phenyl butyl nitrone synergistically repress cyclooxygenase-2 induction in [IL-1beta+Abeta42]-stressed human neural cells.

Interleukin-1beta (IL-1beta) and amyloid-beta peptide 42 (Abeta42) together induce a robust proinflammatory gene expression program in human neural cells in primary culture. One consistent genetic marker for this triggered inflammatory response is an increase in the expression of cycloooxygenase-2 (COX-2), a prostaglandin synthase also found to be up-regulated in neurological disorders such as Alzheimer's disease. In this study we provide data illustrating the combined effect of three independent classes of compounds: the glucocorticoid budesonide epimer R, the platelet-activating factor antagonist LAU-8080, and the free radical scavenger phenyl butyl nitrone, upon COX-2 gene activation and prostaglandin E2 (PGE2) levels in [IL-1beta+Abeta42]-stressed HN cells. The data indicate that specific combinations of repressors of COX-2 activity are synergistic in modulating the stress-induced up-regulation of COX-2 and PGE2, and this may be of potential therapeutic value in the design of treatment for complex neuroinflammatory disorders.

Amyloid beta-Peptides↗
PubMed2005

Matrix metalloproteinase-1 associates with intracellular organelles and confers resistance to lamin A/C degradation during apoptosis.

Since the first description of matrix metalloproteinase (MMP)-1 as an interstitial collagenase, great importance has been ascribed to this enzyme in extracellular matrix remodeling during tumoral, inflammatory, and angiogenic processes. As more evidence for the role of MMPs in targeting nonmatrix substrates emerges, casual observations that intracellular MMP-1 is found in vitro and in vivo prompt investigation of the role that MMP-1 may play on basic cell functions such as cell division and apoptosis. Here we show for the first time that MMP-1 not only has extracellular functions but that it is strongly associated with mitochondria and nuclei and accumulates within the cells during the mitotic phase of the cell cycle. On induction of apoptosis, MMP-1 co-localized with aggregated mitochondria and accumulated around fragmented nuclei. Inhibition of this enzyme by RNA interference or treatment with a broad MMP inhibitor caused faster degradation of lamin A, activation of caspases, and fragmentation of DNA when compared with untreated cells. These observations strongly suggest that intracellular association of MMP-1 to mitochondria and nuclei confers resistance to apoptosis and may explain the well-known association of this enzyme with tumor cell survival and spreading.

Apoptosis↗
PubMed2004

Structural analysis of DNA interactions with biogenic polyamines and cobalt(III)hexamine studied by Fourier transform infrared and capillary electrophoresis.

Biogenic polyamines, such as putrescine, spermidine, and spermine are small organic polycations involved in numerous diverse biological processes. These compounds play an important role in nucleic acid function due to their binding to DNA and RNA. It has been shown that biogenic polyamines cause DNA condensation and aggregation similar to that of inorganic cobalt(III)hexamine cation, which has the ability to induce DNA conformational changes. However, the nature of the polyamine.DNA binding at the molecular level is not clearly established and is the subject of much controversy. In the present study the effects of spermine, spermidine, putrescine, and cobalt(III)hexamine on the solution structure of calf-thymus DNA were investigated using affinity capillary electrophoresis, Fourier transform infrared, and circular dichroism spectroscopic methods. At low polycation concentrations, putrescine binds preferentially through the minor and major grooves of double strand DNA, whereas spermine, spermidine, and cobalt(III)hexamine bind to the major groove. At high polycation concentrations, putrescine interaction with the bases is weak, whereas strong base binding occurred for spermidine in the major and minor grooves of DNA duplex. However, major groove binding is preferred by spermine and cobalt(III)hexamine cations. Electrostatic attractions between polycation and the backbone phosphate group were also observed. No major alterations of B-DNA were observed for biogenic polyamines, whereas cobalt(III)hexamine induced a partial B --> A transition. DNA condensation was also observed for cobalt(III)hexamine cation, whereas organic polyamines induced duplex stabilization. The binding constants calculated for biogenic polyamines are K(Spm) = 2.3 x 10(5) M(-1), K(Spd) = 1.4 x 10(5) M(-1), and K(Put) = 1.02 x 10(5) M(-1). Two binding constants have been found for cobalt(III)hexamine with K(1) = 1.8 x 10(5) M(-1) and K(2) = 9.2 x 10(4) M(-1). The Hill coefficients indicate a positive cooperativity binding for biogenic polyamines and a negative cooperativity for cobalt(III)hexamine.

Binding Sites↗
PubMed2006

Aspirin resistance in coronary artery disease is correlated to elevated markers for oxidative stress but not to the expression of cyclooxygenase (COX) 1/2, a novel COX-1 polymorphism or the PlA(1/2) polymorphism.

Aspirin resistance (AR) is estimated to be present in 5-75% of patients and is related to increased cardiovascular mortality. However, the underlying mechanisms are mostly unknown. In the present study, AR was detected in 14 out of 55 patients (25%) with coronary artery disease. The presence of concomitant anti-inflammatory drugs did not affect AR. Plasma levels of thromboxane B(2) as well as the markers for oxidative stress and known platelet activators 8-isoprostane and lipid peroxidation products were significantly higher in aspirin-resistant individuals (349.3 pg/ml, 53.9 pg/ml, and 538 micromol/l) compared to controls (113.7 pg/ml, 10.3 pg/ml, and 32.2 micromol/l; P < 0.05, respectively). Platelet cyclooxygenase-1 (COX-1) and COX-2 mRNA and protein expression were without significant differences between the two groups. DNA sequencing detected a novel platelet COX-1 single nucleotide polymorphism (SNP) resulting in amino acid exchange at position 8 (Arg8/Trp8). The wild-type as well as the heterozygous and homozygous SNP were present in both patient groups without significant differences. The aspirin binding (Arg120) and acetylation site (Ser529) were unaffected in the samples tested. Neither was AR related to the platelet integrin PlA(1)/A(2) polymorphism. In conclusion, AR appears to be unrelated to differences in platelet COX-1 and COX-2 expression or to a novel platelet COX-1 SNP and the PlA(1)/A(2) SNP. However, a correlation exists to elevated eicosanoids generated by oxidative stress indicating COX-1-independent pathways for the generation of platelet activating molecules represent a potential cause for AR.

Antigens, Neoplasm↗
PubMed1991

Salicylic acid is a systemic signal and an inducer of pathogenesis-related proteins in virus-infected tobacco.

Systemic induction of pathogenesis-related (PR) proteins in tobacco, which occurs during the hypersensitive response to tobacco mosaic virus (TMV), may be caused by a minimum 10-fold systemic increase in endogenous levels of salicylic acid (SA). This rise in SA parallels PR-1 protein induction and occurs in TMV-resistant Xanthi-nc tobacco carrying the N gene, but not in TMV-susceptible (nn) tobacco. By feeding SA to excised leaves of Xanthi-nc (NN) tobacco, we have shown that the observed increase in endogenous SA levels is sufficient for the systemic induction of PR-1 proteins. TMV infection became systemic and Xanthi-nc plants failed to accumulate PR-1 proteins at 32 degrees C. This loss of hypersensitive response at high temperature was associated with an inability to accumulate SA. However, spraying leaves with SA induced PR-1 proteins at both 24 and 32 degrees C. SA is most likely exported from the primary site of infection to the uninfected tissues. A computer model predicts that SA should move rapidly in phloem. When leaves of Xanthi-nc tobacco were excised 24 hr after TMV inoculation and exudates from the cut petioles were collected, the increase in endogenous SA in TMV-inoculated leaves paralleled SA levels in exudates. Exudation and leaf accumulation of SA were proportional to TMV concentration and were higher in light than in darkness. Different components of TMV were compared for their ability to induce SA accumulation and exudation: three different aggregation states of coat protein failed to induce SA, but unencapsidated viral RNA elicited SA accumulation in leaves and phloem. These results further support the hypothesis that SA acts as an endogenous signal that triggers local and systemic induction of PR-1 proteins and, possibly, some components of systemic acquired resistance in NN tobacco.

Immunity, Innate↗
PubMed1989

Stimulation of the growth of metastatic clones of mouse colon adenocarcinoma 26 in vitro by platelet-derived growth factor.

The induction of platelet aggregation by tumor cells was found to be an important determinant for the formation of metastasis of a highly metastatic variant of mouse colon adenocarcinoma 26. We found that the growth of highly metastatic clones, NL-17 and NL-33, of mouse colon 26 was well stimulated by platelet-derived growth factor (PDGF) and the stimulation was dependent on the concentration of the growth factor. The growth of weakly metastatic clones, NL-4 and NL-44, was stimulated marginally by PDGF. Other factors such as transforming growth factor beta and epidermal growth factor did not stimulate the growth of metastatic clones. As the amounts of the receptor of PDGF, as determined by [125I]PDGF binding and mRNA expression, were almost equal in NL-17 and NL-44 clones, the difference in growth potential of these clones after the treatment with PDGF could be explained by post-receptor mechanism(s). The present findings indicate that when tumor cells are arrested in a capillary through the formation of aggregates with platelets, PDGF might play an important role in the establishment of metastasis of mouse colon 26.

Adenocarcinoma↗
PubMed1997

Changes in P2Y1 nucleotide receptor activity during the development of rat salivary glands.

Experiments that used dispersed salivary gland cells from 1-day-old rats indicated the presence of the P2Y nucleotide receptor subtype, P2Y1, based on the agonist potency profile for mobilization of intracellular free Ca2+ [2-methylthio-ATP > ADP > adenosine 5'-O-(2-thiodiphosphate) > ATP, with UTP ineffective] and sequence analysis of reverse transcription-polymerase chain reaction (RT-PCR) products obtained with P2Y1 receptor-specific primers. P2Y1 receptor activity appears to be developmentally regulated, since Ca2+ mobilization in response to the P2Y1-selective agonist, 2-methylthio-ATP, decreased as animal age increased, with the maximal response of 129 +/- 23 nM obtained in 1-day-old animals, decreasing to 30 +/- 3 nM in 4-wk-old animals. However, the abundance of P2Y1 receptor mRNA, assessed by semiquantitative RT-PCR, did not change over this time period, suggesting that receptor activity is regulated by some mechanism other than changes in steady-state levels of P2Y1 receptor mRNA. These findings indicate that functional P2Y1 nucleotide receptors are expressed in immature salivary glands and that receptor activity decreases as the glands mature, suggesting that P2Y1 receptors may have an important role during salivary gland development.

Aging↗
PubMed2002

NCX-4016 (NO-aspirin) inhibits lipopolysaccharide-induced tissue factor expression in vivo: role of nitric oxide.

BACKGROUND: NCX-4016 is an acetylsalicylic acid (ASA) derivative containing a nitric oxide-releasing moiety. Compared with ASA, NCX-4016 has a broader spectrum of antithrombotic and antiinflammatory activities. We hypothesized that NCX-4016 might inhibit in vivo lipopolysaccharide (LPS)-induced expression of tissue factor (TF). METHODS AND RESULTS: Rats were administered 90 mg/kg NCX-4016 orally for 5 days. Placebo, 50 mg/kg ASA, and 80 mg/kg isosorbide-5-mononitrate (ISMN) were used in control groups. On day 5, rats were injected intraperitoneally with 100 microg/kg LPS and killed 6 hours later. The expression of TF in monocytes was measured by flow cytometry and Western blot analysis. Reverse transcriptase-polymerase chain reaction was performed to assess expression of TF and cyclooxygenase-2 (COX-2) genes. Plasma concentrations of interleukin-1beta and tumor necrosis factor-alpha were measured. Urine samples were collected to evaluate the excretion of the thromboxane metabolite 11-dehydro-thromboxane (TX)B2. Gastric mucosa was inspected. LPS injection was followed by synthesis TF and COX-2 mRNAs in circulating monocytes, which were blunted by NCX-4016 but not by ASA or ISMN. Both NCX-4016 and ISMN reduced TF expression on surface of circulating monocyte. LPS increased the excretion 11-dehydro-TXB2, and this was prevented by NCX-4016 and ASA. Unlike ASA, NCX-4016 reduced plasma interleukin-1beta and tumor necrosis factor-alpha. In addition, NCX-4016 almost completely prevented mucosal damage, whereas ASA increased the extension of gastric lesions in LPS-injected rats. CONCLUSIONS: NCX-4016 prevents monocyte TF expression; this is accompanied by inhibition of TX and cytokine biosynthesis. These additive effects of nitric oxide release and COX inhibition may help explain efficacy and tolerability of NCX-4016.

Administration, Oral↗
PubMed1999

Aggregating human platelets stimulate expression of vascular endothelial growth factor in cultured vascular smooth muscle cells through a synergistic effect of transforming growth factor-beta(1) and platelet-derived growth factor(AB).

BACKGROUND: Vascular endothelial growth factor (VEGF), an endothelial mitogen and chemoattractant, has been implicated in the recovery of the endothelium after balloon injury. The increased expression of VEGF in vascular smooth muscle cells (SMC) at sites of injury suggests that this cell type may be a major cellular source of VEGF. This study examined whether aggregating platelets stimulate VEGF expression in cultured SMC. METHODS AND RESULTS: ++VEGF expression in SMC was assessed by Northern blot analysis and by reverse transcription followed by polymerase chain reaction and the release of VEGF by Western blot analysis and immunoassay. Platelet-derived products (PDP) released by aggregating human platelets time-dependently and concentration-dependently enhanced VEGF mRNA levels, mainly that coding for the soluble splice variant VEGF(165/164), and stimulated the release of VEGF protein. These effects were potentiated by transient acidification of PDP, which release bioactive transforming growth factor (TGF)-beta(1), and mimicked by platelet-derived growth factor (PDGF)(AB) and TGF-beta(1) in a synergistic manner. Both a TGF-beta-neutralizing antibody and a PDGF-neutralizing antibody significantly attenuated the effect of acidified PDP on VEGF production. CONCLUSIONS: Aggregating human platelets induce VEGF mRNA expression in cultured SMC and the subsequent release of VEGF protein. This effect can be attributed to a supra-additive action of PDGF(AB) and TGF-beta(1) and may represent a novel mechanism by which platelets contribute to the recovery of the endothelial lining at sites of balloon-injured arteries.

Angioplasty, Balloon↗
PubMed2006

A role for non-muscle myosin II function in furrow maturation in the early zebrafish embryo.

Cytokinesis in early zebrafish embryos involves coordinated changes in the f-actin- and microtubule-based cytoskeleton, and the recruitment of adhesion junction components to the furrow. We show that exposure to inhibitors of non-muscle myosin II function does not affect furrow ingression during the early cleavage cycles but interferes with the recruitment of pericleavage f-actin and cortical beta-catenin aggregates to the furrow, as well as the remodeling of the furrow microtubule array. This remodeling is in turn required for the distal aggregation of the zebrafish germ plasm. Embryos with reduced myosin activity also exhibit at late stages of cytokinesis a stabilized contractile ring apparatus that appears as a ladder-like pattern of short f-actin cables, supporting a role for myosin function in the disassembly of the contractile ring after furrow formation. Our studies support a role for myosin function in furrow maturation that is independent of furrow ingression and which is essential for the recruitment of furrow components and the remodeling of the cytoskeleton during cytokinesis.

Actins↗
PubMedDate not supplied

Intracellular binding sites of acridine orange in living osteosarcoma cells.

There have been many reports concerning the intracellular binding sites of acridine orange (AO), although the actual localization of AO in living cells remains controversial. This study was undertaken to clarify the intracellular localization of AO in living mouse osteosarcoma cells by cytochemical staining. A mouse osteosarcoma cell line (MOS) was cultured and continuously exposed to 0.5 microgram/ml of AO. The intracellular localization and stainability of AO the living tumor cells was morphologically detected by a high resolution fluorescence microscope. To detect the intracellular microstructure, cytochemical staining with rhodamin 123 for mitochondria, acid phosphatase for lysosome, Sudan-black for fat vesicle and toluidine blue for glucosaminoglycan were performed using fixed cells. The results showed that both the nucleus and cytoplasm of tumor cells at 10 minutes after exposure to 0.5 microgram/ml of AO emitted green fluorescence, which was especially intense in the nucleolus, but not brilliant in the nucleus and was granular orange to red fluorescence in the perinuclear particles. This stainability of AO was different from that of rhodamin 123, Sudan-black or toluidine blue, but similar to that of acid phosphatase. Based on these results, we conclude that the green fluorescence may have derived from AO binding to double stranded RNA, not to DNA, and that orange fluorescence may have derived from aggregated AO binding to lysosome.

Acid Phosphatase↗
PubMed2003

Effects of ATP, Mg2+ and a mixture of the two on the formation of large DNA aggregates induced by spermidine.

To investigate the effects of ATP, Mg2+, and a mixture of the two on the formation of large DNA aggregates induced by spermidine, we constructed novel phase diagrams of the spermidine/DNA/Tris-buffer system in the presence of these compounds. These diagrams reveal not only the difference in the inhibition of the aggregate formation between ATP and Mg2+ but also a type of buffering effect whereby the complex formation of ATP and Mg2+ diminishes their individual inhibitory actions. Furthermore, the equilibrium composition of ATP, spermidine, Mg2+, and their complexes in the liquid phase was estimated using the equilibrium constants for the complex formations and their mass balances. From this solution equilibrium analysis, the threshold condition for DNA aggregation is suggested. The phase diagrams and equilibrium analysis presented here are useful to predict the threshold of aggregation in a system similar to in vitro transcription. Finally, we recommend that region b in this paper, where the variation in the concentration of either ATP or Mg2+ had little effect on the DNA aggregation, should be used to establish the initial conditions of in vitro RNA synthesis.

Journal Article↗
PubMed1990

[Covalent-bound aggregates of equine venezuelan encephalomyelitis virus induced by UV-irradiation].

Formation of Venecuelan equine encephalomyelitis virus (VEE) aggregates induced by UV-light has been studied. The high doses of UV-irradiation induced the protein-protein cross-links resulting in formation of fast sedimenting viral structures. The latter structures are supposed to be presented by the aggregates of several virions linked by the UV-light induced RNA-protein and protein-protein covalent bonds. The lesions in the fine structure of virion envelope was registered by the electron microscopy technique.

Encephalitis Virus, Venezuelan Equine↗
PubMed2001

Segregation of nucleolar components coincides with caspase-3 activation in cisplatin-treated HeLa cells.

We studied morphological changes of the nucleoli in HeLa cells treated with cisplatin and compared them with induction of markers of programmed cell death and TUNEL staining. We used different light microscopic nucleolar staining methods allowing us to visualize not only nucleolar proteins but also nucleolar RNA. Our results show predominantly compact, centrally localized nucleoli in intact control HeLa cells. In cisplatin-treated HeLa cells, we found an early onset of nucleolar segregation of proteins detected by argyrophilic nucleolar organizer regions and anti-nucleolar monoclonal antibody as well as an increased immunoreactivity for activated caspase-3 after 6 hours. Staining with Toluidine Blue and Methyl-green Pyronine revealed segregated nucleoli 12 hours after the treatment with cisplatin. TUNEL positivity in cisplatin-treated HeLa cells was accompanied by the aggregation of the argyrophilic proteins in the central portion of nucleus, disappearance of nucleolar RNA and shrinkage of the nucleus after 24 hours. Monitoring of the biochemical changes by immunoblotting revealed that activation of distinct caspases and degradation of their downstream protein substrates is executed in two phases. During an early apoptotic stage beginning 4.5 hours post treatment an activation of caspase-9 and caspase-3 was observed. This was accompanied by proteolytic cleavage of poly(ADP-ribose) polymerase-1 (PARP-1). The caspase-9 activation seems to be mediated by recruitment by the activating factor Apaf-1 because the increased accumulation of Apaf-1 and cytochrome C in cytosol preceded the generation of mature caspase-9 form. A second phase of apoptosis occurring between 10 and 15 hours post treatment was characterized by degradation of other nucleolar and nuclear proteins such as nuclear lamins, topoisomerase I and B23. In conclusion, remarkable segregation of nucleolar argyrophilic proteins, nucleolar RNA and a simultaneous activation of the cascade of caspases markedly preceded the TUNEL positivity in cisplatin-treated HeLa cells thereby substantiating the hypothesis that the nucleolus is a preferred target for caspase-3-dependent proteolysis in cisplatin-treated HeLa cells.

Apoptosis↗