Serum S100A8/A9 and S100A12 Levels in Children With Polyarticular Forms of Juvenile Idiopathic Arthritis: Relationship to Maintenance of Clinically Inactive Disease During Anti-Tumor Necrosis Factor Therapy and Occurrence of Disease Flare After Discontinuation of Therapy

OBJECTIVE

To determine the relationship between serum levels of S100A8/A9 and S100A12 and the maintenance of clinically inactive disease during anti-tumor necrosis factor (anti-TNF) therapy and the occurrence of disease flare following withdrawal of anti-TNF therapy in patients with polyarticular forms of juvenile idiopathic arthritis (JIA).

METHODS

In this prospective, multicenter study, 137 patients with polyarticular-course JIA whose disease was clinically inactive while receiving anti-TNF therapy were enrolled. Patients were observed for an initial 6-month phase during which anti-TNF treatment was continued. For those patients who maintained clinically inactive disease over the 6 months, anti-TNF was withdrawn and they were followed up for 8 months to assess for the occurrence of flare. Serum S100 levels were measured at baseline and at the time of anti-TNF withdrawal. Spearman's rank correlation test, Mann-Whitney U test, Kruskal-Wallis test, receiver operating characteristic (ROC) curve, and Kaplan-Meier survival analyses were used to assess the relationship between serum S100 levels and maintenance of clinically inactive disease and occurrence of disease flare after anti-TNF withdrawal.

RESULTS

Over the 6-month initial phase with anti-TNF therapy, the disease state reverted from clinically inactive to clinically active in 24 (18%) of the 130 evaluable patients with polyarticular-course JIA; following anti-TNF withdrawal, 39 (37%) of the 106 evaluable patients experienced a flare. Serum levels of S100A8/A9 and S100A12 were elevated in up to 45% of patients. Results of the ROC analysis revealed that serum S100 levels did not predict maintenance of clinically inactive disease during anti-TNF therapy nor did they predict disease flare after treatment withdrawal. Elevated levels of S100A8/A9 were not predictive of the occurrence of a disease flare within 30 days, 60 days, 90 days, or 8 months following anti-TNF withdrawal, and elevated S100A12 levels had a modest predictive ability for determining the risk of flare within 30, 60, and 90 days after treatment withdrawal. Serum S100A12 levels at the time of anti-TNF withdrawal were inversely correlated with the time to disease flare (r = -0.36).

CONCLUSION

Serum S100 levels did not predict maintenance of clinically inactive disease or occurrence of disease flare in patients with polyarticular-course JIA, and S100A12 levels were only moderately, and inversely, correlated with the time to disease flare.

Risk, Timing, and Predictors of Disease Flare After Discontinuation of Anti-Tumor Necrosis Factor Therapy in Children With Polyarticular Forms of Juvenile Idiopathic Arthritis With Clinically Inactive Disease

OBJECTIVE

To determine the frequency, time to flare, and predictors of disease flare upon withdrawal of anti-tumor necrosis factor (anti-TNF) therapy in children with polyarticular forms of juvenile idiopathic arthritis (JIA) who demonstrated ≥6 months of continuous clinically inactive disease.

METHODS

In 16 centers 137 patients with clinically inactive JIA who were receiving anti-TNF therapy (42% of whom were also receiving methotrexate [MTX]) were prospectively followed up. If the disease remained clinically inactive for the initial 6 months of the study, anti-TNF was stopped and patients were assessed for flare at 1, 2, 3, 4, 6, and 8 months. Life-table analysis, t-tests, chi-square test, and Cox regression analysis were used to identify independent variables that could significantly predict flare by 8 months or time to flare.

RESULTS

Of 137 patients, 106 (77%) maintained clinically inactive disease while receiving anti-TNF therapy for the initial 6 months and were included in the phase of the study in which anti-TNF therapy was stopped. Stopping anti-TNF resulted in disease flare in 39 (37%) of 106 patients by 8 months. The mean/median ± SEM time to flare was 212/250 ± 9.77 days. Patients with shorter disease duration at enrollment, older age at onset and diagnosis, shorter disease duration prior to experiencing clinically inactive disease, and shorter time from onset of clinically inactive disease to enrollment were found to have significantly lower hazard ratios for likelihood of flare by 8 months (P < 0.05).

CONCLUSION

Over one-third of patients with polyarticular JIA with sustained clinically inactive disease will experience a flare by 8 months after discontinuation of anti-TNF therapy. Several predictors of lower likelihood of flare were identified.

High Levels of DEK Autoantibodies in Sera of Patients With Polyarticular Juvenile Idiopathic Arthritis and With Early Disease Flares Following Cessation of Anti-Tumor Necrosis Factor Therapy

OBJECTIVE

The nuclear oncoprotein DEK is an autoantigen associated with juvenile idiopathic arthritis (JIA), especially the oligoarticular subtype. DEK is a secreted chemotactic factor. Abundant levels of DEK and DEK autoantibodies are found in inflamed synovium in JIA. We undertook this study to further characterize the nature of DEK autoantibodies in screening serum samples from 2 different cohorts that consisted mostly of patients with JIA.

METHODS

DEK autoantibody levels were analyzed in sera from 33 JIA patients, 13 patients with other inflammatory conditions, and 11 healthy controls, as well as in 89 serum samples from JIA patients receiving anti-tumor necrosis factor (anti-TNF) therapy. Recombinant His-tagged full-length DEK protein (1-375 amino acids [aa]) and the 187-375-aa and 1-350-aa His-tagged DEK fragments made in a baculovirus system were used for enzyme-linked immunosorbent assay (ELISA) and immunoblotting. The C-terminal 25-aa fragment of DEK was expressed in a glutathione S-transferase-tagged vector. ELISA results were calculated as area under the curve by the trapezoidal rule.

RESULTS

DEK autoantibody levels were significantly higher in patients with polyarticular JIA than in those with oligoarticular JIA, and were higher in patients with polyarticular JIA who had more active disease after cessation of anti-TNF therapy. Immunoblotting against the C-terminal 25-aa fragment of DEK confirmed that this section of the DEK molecule is the most immunogenic domain.

CONCLUSION

DEK autoantibody levels are higher in patients with polyarticular JIA than in those with oligoarticular JIA, and higher in patients who have disease flares after cessation of anti-TNF therapy. The C-terminal 25-aa fragment is the most immunogenic portion of DEK. These findings are significant with respect to the nature of DEK autoantibodies, their contribution to JIA pathogenesis, and their implications for JIA management.

Safety of celecoxib and nonselective nonsteroidal anti-inflammatory drugs in juvenile idiopathic arthritis: results of the Phase 4 registry

BACKGROUND

This study aimed to assess long-term safety and developmental data on juvenile idiopathic arthritis (JIA) patients treated in routine clinical practice with celecoxib or nonselective nonsteroidal anti-inflammatory drugs (nsNSAIDs).

METHODS

Children aged ≥2 to <18 years with rheumatoid-factor-positive or -negative polyarthritis, persistent or extended oligoarthritis, or systemic arthritis were enrolled into this prospective, observational, multicenter standard-of-care registry. Eligible patients were newly or recently prescribed (≤6 months) an nsNSAID or celecoxib. Enrolled patients were followed to the end of the study, whether they remained on the original NSAID, switched, or discontinued therapy altogether. All adverse events (AEs) regardless of severity were captured in the database.

RESULTS

A total of 274 patients (nsNSAID, n = 219; celecoxib, n = 55) were observed for 410 patient-years of observation. Naproxen, meloxicam, and nabumetone were the most frequently used nsNSAIDs. At baseline, the celecoxib group was older, had a numerically longer median time since diagnosis, and a numerically higher proportion of patients with a history of gastrointestinal-related NSAID intolerance. AEs reported were those frequently observed with NSAID treatment and were similar across groups (nsNSAIDs: 52.0%; celecoxib: 52.9%). Twelve unique patients experienced a total of 18 serious AEs; the most frequent were infections, and none was attributed to NSAID use.

CONCLUSIONS

The safety profile of celecoxib and nsNSAIDs appears similar overall. The results from this registry, ongoing pharmacovigilance, and the phase 3 trial that led to the approval of celecoxib for children with JIA provide evidence that the benefit-risk for celecoxib treatment in JIA remains positive.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT00688545.

Disappearing enhancing brain lesion in a child with neurofibromatosis type I

Neurofibromatosis type 1 (NF1) in children can produce a variety of parenchymal signal abnormalities on cranial MR. Areas of abnormal signal in these patients may represent regions of disordered myelination, "hamartomatous" change or frank neoplasia. The presence of contrast enhancement in intracranial lesions in patients with NF1 is usually strongly suggestive of tumor. We report the case of a child with NF1 and a focal enhancing brain parenchymal lesion which spontaneously resolved without specific therapy.

Naturally occurring active N-domain of human angiotensin I-converting enzyme

Angiotensin I-converting enzyme (ACE, kininase II) is a single-chain protein containing two active site domains (named N- and C-domains according to position in the chain). ACE is bound to plasma membranes by its C-terminal hydrophobic transmembrane anchor. Ileal fluid, rich in ACE activity, obtained from patients after surgical colectomy was used as the source. Column chromatography, including modified affinity chromatography on lisinopril-Sepharose, yielded homogeneous ACE after only a 45-fold purification. N-terminal sequencing of ileal ACE and partial sequencing of CNBr fragments revealed the presence of an intact N terminus but only a single N-domain active site, ending between residues 443 and 559. Thus, ileal-fluid ACE is a unique enzyme differing from the widely distributed two-domain somatic enzyme or the single C-domain testicular (germinal) ACE. The molecular mass of ileal ACE is 108 kDa and when deglycosylated, the molecular mass is 68 kDa, indicating extensive glycosylation (37% by weight). In agreement with the results reported with recombinant variants of ACE, the ileal enzyme is less Cl(-)-dependent than somatic ACE; release of the C-terminal dipeptide from a peptide substrate was optimal in only 10 mM Cl-. In addition to hydrolyzing at the C-terminal end of peptides, ileal ACE efficiently cleaved the protected N-terminal tripeptide from the luteinizing hormone-releasing hormone and its congener 6-31 times faster, depending on the Cl- concentration, than the C-domain in recombinant testicular ACE. Thus we have isolated an active human ACE consisting of a single N-domain. We suggest that there is a bridge section of about 100 amino acids between the active N- and C-domains of somatic ACE where it may be proteolytically cleaved to liberate the active N-domain. These findings have potential relevance and importance in the therapeutic application of ACE inhibitors.

Sequencing and cloning of human prolylcarboxypeptidase (angiotensinase C). Similarity to both serine carboxypeptidase and prolylendopeptidase families

Prolylcarboxypeptidase, a lysosomal serine carboxypeptidase, cleaves COOH-terminal amino acids linked to proline, as in angiotensin II and III and [des-Arg9] bradykinin. About 25% of the enzyme protein was sequenced, and the complete sequence was deduced from its human kidney cDNA. The cDNA insert contained an open reading frame of 1488 base pairs coding for a protein of 496 residues. The authentic NH2-terminal sequence matched the deduced protein sequence starting with residue 46, suggesting the presence of both a signal and propeptide. The mature enzyme (451 residues) has a calculated M(r) = 51,043, whereas the M(r) of the purified glycoprotein is 58,000, indicating 12% carbohydrate. The overall sequence identity with serine peptidases is low (10-18%), but sequences around residues of the putative catalytic triad (Ser134, Asp333, His411) are similar (30-67%) to both the serine carboxypeptidases (e.g. deamidase or lysosomal protective protein, yeast carboxypeptidase Y, and KEX1 gene product) and the prolylendopeptidase family. Thus, prolylcarboxypeptidase links these two families, suggesting an evolutionary relationship. It is inhibited (Ki = 2.6 x 10(-7) M) by benzyloxycarbonyl-Pro-prolinal, a specific inhibitor of prolylendopeptidase, another angiotensin metabolizing enzyme. Prolylcarboxypeptidase contains serine or threonine residues repeated as the 26th residue 7 out of 9 times, with identical or similar amino acids in other positions in the repeats. The KEX1 gene product contains a similar motif, with serine or threonine as every 27th residue. The importance of prolylcarboxypeptidase is strongly suggested by its presence in various organs and cells and by the substrates it cleaves.

Inactivation of endothelin-1 by an enzyme of the vascular endothelial cells

We previously investigated the inactivation of endothelin-1 by deamidase (lysosomal protective protein), present in many cells, including vascular smooth muscle cells. This enzyme, which we originally purified from human platelets, preferentially hydrolyzes peptides at the C-terminus with hydrophobic amino acids in the P1 or P1' position or both and thereby inactivates endothelin-1, which has a C-terminal sequence of Ile19-Ile20-Trp21-OH. We tested for the presence of deamidase in cultured bovine aortic endothelial cells. The final supernatant of the homogenized cells (S3) cleaved the deamidase substrate dansyl-Phe-Leu-Arg at a rate of 1.3 nmol/min per 10(6) cells at pH 5.5 at 37 degrees C. Endothelin-1 was completely inactivated by the S3 fraction as determined on rat thoracic aorta strips. The major site of inactivation was the Ile20-Trp21 bond, established by high performance liquid chromatography and by amino acid analysis where the main product was des-Trp21-endothelin-1. The hydrolysis of endothelin-1 (5.9 nmol/min per milligram of protein at pH 5.5 at 23 degrees C) by S3 was blocked mainly by inhibitors of deamidase, including diisopropyl fluorophosphate, but not by inhibitors of some other peptidases. This is the first report of a novel pathway of endothelin-1 metabolism in endothelial cells. Thus, endothelial cells, besides being the source of endothelin-1, contain an enzyme that inactivates it.

Chloroplast and cytoplasmic enzymes: isolation and sequencing of cDNAs coding for two distinct pea chloroplast aldolases

Two cDNAs which correspond to two very similar Class I aldolases have been isolated from a pea (Pisum sativum L.) cDNA library. With the exception of one codon they match the experimentally determined N-terminal sequence of a pea chloroplast aldolase. The deduced C-terminal sequence of one of these clones is unique among Class I aldolases. The deduced C-terminus of the other is more like the C-terminus of other eucaryotic Class I aldolases. Comparisons of sequence homology suggest that the pea chloroplast isozymes are only marginally more closely related to the anaerobically induced plant aldolases than to aldolases from animals.

Amino acid sequences of several Bacillus subtilis proteins modified by apparent guanylylation

Bacillus subtilis cell extracts, prepared at different times during growth, contained several proteins that were apparently guanylylated in vitro with [alpha-32P]-GTP. Four of the proteins were partially purified and the N-terminal amino acid sequences (13 to 20 residues) were determined. One sequence had 84% identity to Bacillus stearothermophilus triosephosphate isomerase, two were 100% identical to the predicted sequences of the B. subtilis ptsI and ptsH genes while no identity was found for the fourth sequence. This apparent guanylylation occurred with proteins involved in glucose metabolism, although the significance is unknown.

The amino acid sequence of a Bacillus subtilis phosphoprotein that matches an orfY-tsr coding sequence

Bacillus subtilis contains a 30 kDa protein which was phosphorylated during late vegetative growth and sporulation. The sequence for the N-terminal 16 amino acids was found to be identical to the predicted sequence for the N-terminus of a small open reading frame, orfY, but diverged from the predicted sequence thereafter. The orfY region was resequenced and contained one less adenine residue than previously reported, resulting in an open reading frame from within orfY through the entire coding region for tsr which follows orfY. The predicted orfY-tsr amino acid sequence showed 24% identity to Escherichia coli fructose-1,6-bisphosphate aldolase. Two mutants in the tsr region had 2-5% of wild-type aldolase and the nucleotide sequences showed missense mutations. These results indicate that orfY-tsr encodes aldolase and should be renamed fba1.

Identification of proteins phosphorylated by ATP during sporulation of Bacillus subtilis

Protein phosphorylation in Bacillus subtilis was assayed in vitro by using extracts prepared from cells at various times during growth and sporulation. At least six proteins were labeled in vitro by using [gamma-32P]ATP and extracts of vegetative cells. In extracts prepared at the end of exponential growth and during stationary phase, 12 to 13 proteins were labeled. Seven of the phosphoproteins were purified by fast-performance liquid chromatography and polyacrylamide gel electrophoresis, blotted to Immobilon membranes, and subjected to partial protein sequencing. One of the sequences had sequence homology (greater than 45%) to elongation factor G from several bacterial species, and four sequences matched the predicted amino-terminal sequences of the outB, orfY-tsr, orfU, and ptsH genes.

Inactivation of endothelin I by deamidase (lysosomal protective protein)

Deamidase cleaves ester and peptide bonds in various substrates and deamidates protected COOH-terminal amino acids. It preferentially hydrolyzes peptides which contain hydrophobic amino acids in the P1' and/or P1 position. Because the COOH-terminal end of endothelin I contains the hydrophobic sequence -Ile19-Ile20-Trp21-OH, we investigated whether human deamidase, purified from platelets, could inactivate this peptide. We found that deamidase readily cleaved off Trp21 with an acid pH optimum, a Km = 22 microM, a kcat of 1454 min-1, and a kcat/Km of 68 microM-1 min-1. We also found the enzyme to be present in target cells of endothelin, in vascular smooth muscle cells. Extracts of cultured vascular smooth muscle cells cleave both the synthetic fluorescent substrate 5-dimethylaminonaphthalene-1-sulfonyl(Dns)-Phe-Leu-Arg and endothelin I by releasing the COOH-terminal amino acid. The reaction was inhibited by diisopropyl fluorophosphate, benzyloxycarbonyl-Gly-Leu-Phe-CH2Cl, and p-chloromercuribenzenesulfonate, which inhibit the purified deamidase, but not by inhibitors of some other peptidases. The rate of hydrolysis of endothelin I in the soluble, 100,000 x g final supernatant of the homogenized smooth muscle cells was 2.1 mumol/h/mg and 3.1 mumol/h/mg for Dns-Phe-Leu-Arg. Thus, smooth muscles, platelets, and many other tissues which contain the deamidase can inactivate endothelin by cleaving the COOH-terminal tryptophan.

Production of the rat type 1 insulin-like growth factor-binding protein by well differentiated H4EIIC3 hepatoma cells: identification, purification, and N-terminal amino acid analysis

We recently identified a 32 K mol wt insulin-like growth factor (IGF)-binding protein (BP) which is markedly increased in the serum of streptozotocin-diabetic rats and recognized by antiserum against the human amniotic fluid IGFBP (hIGFBP-1). In the present study we sought to confirm that this protein represents the rat homolog of IGFBP-1 (rIGFBP-1), and that rIGFBP-1 may, therefore, play an important role in the regulation of IGF bioactivity in experimental diabetes. Since the abundance of related hepatic mRNA is high in diabetic rats, we asked whether well differentiated H4EIIC3 rat hepatoma cells produce rIGFBP-1 and provide sufficient amounts of this protein for purification and further characterization. Specific IGF-binding activity in hepatoma conditioned medium was detected initially by incubation with 125I-labeled recombinant human IGF-II and precipitation with polyethylene glycol. Ligand blotting demonstrated a 32 K BP, identical in size to the major low mol wt IGFBP found in diabetic rat serum. Affinity labeling and immunoprecipitation confirmed that this BP is related to human IGFBP-1 and is distinct from the fetal rat IGFBP, rIGFBP-2. Incorporation of [35S]methionine into 32 K BPs confirmed synthesis by hepatoma cells. For purification of BPs, conditioned medium was collected in roller culture, and BPs were purified by ammonium sulfate precipitation, Sephadex G-75 chromatography, and reverse phase HPLC. Partial amino acid sequencing of purified protein demonstrated 68% identity with the human IGFBP-1 and distinguished this BP from previously characterized rat IGFBPs. Purified protein bound both IGF-I and IGF-II with high affinity. We conclude that the 32 K IGFBP produced by H4EIIC3 hepatoma cells in culture represents the rat form of IGFBP-1 (rIGFBP-1). Regulation of rIGFBP-1 may play an important role in the modulation of IGF bioactivity in experimental animals with metabolic disease. The availability of purified rIGFBP-1 and identification of a cell line that produces this BP will greatly facilitate future studies of IGFBP-1 in the rat model.

Separation of nucleosides and nucleotides by reversed-phase high-performance liquid chromatography with volatile buffers allowing sample recovery

Reversed-phase high-performance liquid chromatography using a C18 column with volatile buffers as the eluant was applied to the separation of a number of nucleosides and nucleotides. Groups of seven nucleosides and five nucleoside monophosphates were separated isocratically employing 0.1 M trimethylammonium acetate and 2% acetonitrile at pH 7.0. Groups of seven nucleoside diphosphates and seven nucleoside triphosphates were separated with 0.1 M triethylammonium bicarbonate and 2% acetonitrile titrated to a pH of 7.1 with acetic acid. The techniques described give resolution and separations comparable to nonvolatile buffers. Moreover, the eluant trimethylammonium acetate or triethylammonium bicarbonate buffer can easily be removed in vacuo from the column effluent, making the technique useful for preparative separations of these compounds. The observed elution pattern of nucleoside phosphates suggests that "paired-ion" chromatography is involved in the separation.

2,4-Dinitrophenylhydrazone formation at the aldehyde derived by periodate cleavage of alpha-amanitin

10(-4) cleavage of alpha-amanitin after the procedure of Wieland & Fahrmeir (1) but without prior protective methylation of the 6'-hydroxyl of the tryptophan residue affords the alpha-amanitin aldehyde in 45% yield. The aldehyde was found to exhibit Ki = 3.0 and 12 microM for Drosophila melanogaster and wheat germ RNA polymerase II, respectively. This value is approximately 100-fold greater than for the parent alpha-amanitin. Treatment of the alpha-amanitin aldehyde with 2,4-dinitrophenylhydrazine in CH3OH, CH3CN, or dimethylsulfoxide yielded three products. Two of these did not contain the 2,4-dinitrophenyl moiety, showed Ki = 3.3 and 0.26 microM for wheat germ RNA polymerase II (alpha-amanitin, Ki = 0.09 microM), and accounted for 30-60% and 3% of the input alpha-amanitin aldehyde, respectively. The alpha-amanitin-2,4 dinitrophenylhydrazone was recovered in less than 10% yield regardless of reaction condition and showed a Ki = 0.26 microM on wheat germ RNA polymerase II. This hydrazone establishes that the amatoxin molecule can be modified in the dihydroxyisoleucine residue without disruption of binding to the RNA polymerase.

Putative function of Drosophila melanogaster heat shock proteins in the nucleoskeleton

The cellular distribution in Drosophila Kc cells of [35S]methionine-labeled heat shock proteins has been examined by 0.2% Nonidet P-40-mediated cell lysis and Na-deoxycholate-Tween 40 extraction of the nuclei. The 83,000-dalton heat shock protein was limited to the detergent extracts while the remaining heat shock proteins were found both in a soluble pool in the detergent extracts and in a bound pool in the nuclei. The bound pool included the 70,000-68,000-, 27,000-, 26,000-, 23,000-, and 21,000-dalton heat shock proteins; these proteins accumulated in the nuclei during the time course of heat shock as assayed by [35S]methionine labeling and dye binding on gel electropherograms. DNA and histone-depleted nuclei were prepared by extensive nuclease digestion, 2.0 M NaCl extraction, and sedimentation of the original detergent-washed nuclei. Of the 35S-labeled bound pool, 69% remained associated in a rapidly sedimenting complex that retained only approximately 5% of the DNA. Thus, the binding of the 70,000-68,000-, 27,000-, 26,000-, 23,000-, and 21,000-dalton heat shock proteins appeared primarily to be with the nuclear scaffold rather than the chromatin. We conclude from the mass of heat shock protein synthesis that these proteins probably are structural elements of the nucleus.

alpha-Amanitin: inactivation by bovine lactoperoxidase

The principle amatoxin, alpha-amanitin, is found to be extremely sensitive toward lactoperoxidase catalyzed degradation, rather than iodination, of the indole nucleus. Extensive attenuation of inhibitor potency against eukaryotic DNA-dependent RNA polymerase II accompanies the treatment of alpha-amanitin with lactoperoxidase, iodide and hydrogen peroxide.

Ribonucleotidyl transferase in preparations of partially purified DNA polymerase alpha of the sea urchin

Three ribonucleotidyl transferase types have been described in the sea urchin: riboadenylate trnasferase, the DNA dependent RNA polymerases, and a DNA polymerase associated ribonucleotidyl transferase (Biochemistry 15:3106-3113, 1976). In the present work this latter ribonucleotidyl transferase was found to purify with DNA polymerase alpha through phosphocellulose, DEAE-Sephadex and DNA cellulose and to cosediment at 6.5 S. This ribonucleotidyl transferase was active with Mn+2, but not Mg+2, on calf thymus DNA and poly(dC). Other synthetic templates elicited DNA polymerase alpha but no ribonucleotidyl transferase activity. From alkaline hydrolysates of the poly(dC) directed GTP polymerization, we found Goh and Gp in a ratio of 1:16 indicating an average chain length of 17 residues after a 20 min reaction. Co-polymerization of GTP (5 micrometer) and dGTP (10 micrometer) yielded a non-random distribution of the ribonucleotide in the deoxyribonucleotide. The properties of this urchin ribonucleotidyl transferase are unlike any previously described eukaryotic transferase and the data is discussed with reference to the known properties of E. coli DNA polymerase I and the primase.

DNA polymerase alpha and beta in the California urchin

DNA polymerase alpha and beta were identified in the urchin, Strongylocentrotus purpuratus. The DNA polymerase beta sedimented at 3.4 S, constituted 5% of total DNA polymerase activity, and was resistant to N-ethylmaleimide and high ionic strength. The polymerase alpha sedimented at 6--8 S, was inhibited by N-ethylmalemide or 0.1 M (NH4)2SO4, and was dependent upon glycerol for preservation of activity. Both the polymerases alpha and beta were nuclear associated in embryos. The DNA polymerase alpha was markedly heterogeneous on DEAE-Sephadex ion exchange and showed three modal polymerase species. These polymerase alpha species were indistinguishable by template activity assays but the DNA polymerase associated ribonucleotidyl transferase (Biochemistry 75 : 3106-3113, 1976) was found predominantly with only one of the DNA polymerase alpha species.

Biochemistry of the amatoxins: preparation and characterization of a stably iodinated alpha-amanitin

Iodination of alpha-amanitin at the 7-position in the 6-hydroxy-2-sulfoxytryptophan moiety is effected with 1 equiv of iodine monochloride in methanol. The isolated product shows a lambdamax in methanol at 301 nm, compared with 305 nm for the parent alpha-amanitin; in methanolic 0.01 M NaOH the lambdamax are 330 and 332 nm for the product and parent, respectively. Spectrophotometric titration of the phenolic hydroxyl shows a decrease in pKa from 9.72 (alpha-amanitin) to 7.94 (7 iodo-alpha-amanitin). Appropriate spectrophotometric examination therefore distinguishes between parent and product. Proton magnetic resonance shows two aromatic protons (v4H = 7.57; V5H = 6.90 ppm; j4,5 = 9) in the 7-iodo-alpha-amanitin and three aromatic protons (v4H = 7.64; V5H = 6.78; V7H = 6.94 ppm; j4,5 = 9; J5,7 = 2) in alpha amanitin thus establishing the extent and position of iodine substitution. The 7-iodo-alpha-amanitin effectively inhibits RNA polymerase activity with half-maximal inhibition at 2 X 10(-9) M and 10(-4) M for the sea urchin RNA polymerases II and III, respectively. Addition of [125I]-7-iodo-alpha-amanitin (200 Ci/mmol) to crude extracts from sea urchin blastula, MOPC 315 plasmacytoma, and adult Oregon R Drosophila melanogaster followed by resolution on DEAE-Sephadex demonstrates that the radioactive ligand binds stably and specifically with RNA polymerase II in each of these extracts.

Nucleic acid polymerizing enzymes in developing Strongylocentrotus franciscanus embryos

DNA-dependent RNA polymerase, DNA-Dependent DNA polymerase, and terminal riboadenylate transferase (TRT) activities have been measured after DEAE-Sephadex chromatography of whole cell extracts prepared from eggs and staged embryos of the urchin, Stronglyocentrotus franciscanus. Activity of each of these three polymerase classes is present in the egg, and the total activity per embryo is constant throughout embryogenesis to the pluteus stage (approximately 1000 cells). Thus the egg appears to contain sufficient DNA polymerase, RNA polymerase, and TRT TRT for embryogenesis. The increases in the synthesis of DNA, RNA and polyadenylated RNA tracts observed after fertilization must be due to the activation of the preexisting egg enzymes. Separation of the egg into nucleate and anucleate halves demonstrates that the RNA polymerases are not restricted to the egg nucleus. During development, the enzymes become progressively more associated with the cell nucleus. The egg extracts contain low activities (approximately 6% total) of RNA polymerase II as measured by sensitivity to alpha-amanitin. This is confirmed by resolution of the RNA polymerase forms I, II, and III by gradient sievorptive elution on DEAE-Sephadex. Later stage embryos contain more nearly equal activities of RNA polymerase, I, II, and III, although the total RNA polymerase activity per embryo is not changed. Additionally, two chromatographicallly distinct species of RNA polymerase III are detected, one of which is observed only in later stages. Thus interconversion of enzymes via addition of new subunits or coordinate synthesis and loss of enzyme species must occur.

Specific inhibition of nuclear RNA polymerase II by alpha-amanitin

alpha-Amanitin, a toxic substance from the mushroom Amanita phalloides, is a potent inhibitor of DNA-dependent RNA polymerase II (the nucleoplasmic form) from sea urchin, rat liver, and calf thymus. This compound exerts no effect on the activity of polymerase I (nucleolar form) or polymerase III (also nucleoplasmic). The inhibition is due to a specific interaction with polymerase II or with a complex of DNA and polymerase II.