Effects of metals on the binding of protein factors to the mouse 2',5'-oligoadenylate synthetase ME-12 gene regulatory region

We have previously demonstrated that using mouse 2',5'-oligoadenylate synthetase (2-5A synthetase) gene (ME-12) regulatory region AB as a probe, at least six complexes (C1-C6) can be detected by the mobility shift electrophoresis assay with extracts of murine BALB/c-3T3 cells. The formation of these complexes is greatly influenced by different buffer conditions and the presence of metals. C1 and C4 signals are stronger in Tris-HCl buffer than in phosphate buffer in the absence of added metals. Both Na+ and Mg2+ facilitate C1, C3, and C4 formation. Na+ also facilitates C3 and C4 formation with the interferon (IFN) response element B. Na+ has little effect on C2 formation with the regulatory region AB, whereas presence of Mg2+ at low concentrations gives a strong C2 signal. A new band, C7, was detected in the presence of 50 or 100 mM Na+. A relatively high Mg2+ concentration is required for C5 formation and Mg2+ interferes with C6 and C7 formation. Cu2+ and Zn2+ markedly inhibit formation of most complexes. However, a new band forms in 0.15 mM Cu2+ when 10 mM Mg2+ was also present. Co2+ enhances C2b and C3 formation and inhibits C4 formation. Mn2+ enhances C3, C1, and C2 formation to different degrees and inhibits C4 formation. At 0.15 and 0.25 mM, Mn2+ generates a new band. In competition experiments between Cu2+ and Mg2+, Cu2+ strongly inhibited Mg2+ effects on complex formation, except that 0.15 or 0.25 mM Cu2+ enhanced the C2a and C2b signals.

Protein factors that bind to the murine 2',5'-oligoadenylate synthetase ME-12 gene 5' upstream regulatory region

The murine 2',5'-oligoadenylate synthetase ME-12 gene regulatory region AB forms six complexes with protein factors in murine BALB/c 3T3 cells as demonstrated by the mobility shift electrophoresis assay under the reaction conditions used. The complexes, designated C1-C6 in order of their decreasing electrophoretic mobility, showed three distinctive specificities with regulatory region AB, element A, and element B as probes or competing DNA: 1) C1 is region AB-specific (this complex did not form with either element A or B used alone or as a mixture); 2) C5 formed both with element A and element B; 3) C2, C3, C4, and C6 formed with element B, but not A. The protein factors that give rise to these complexes show differential DNA binding activities in various buffer solutions at different pH values. The C4-forming protein factor is the interferon (IFN)-alpha/beta-stimulated response factor (ISRF) which shows element B specificity. It preexists in the cytoplasm. ISRF appears to be complexed to an inhibitor (ISRFI) in the cytoplasm and to dissociate from the inhibitor and to translocate into the nucleus upon treatment of cells with IFN-alpha/beta. We propose that IFN-alpha/beta treatment of BALB/c 3T3 can trigger at least two events: 1) loosening of a tight inhibitor-ISRF complex with the release of free ISRF; this may be mediated via phosphorylation of ISRF or ISRFI; 2) translocation of ISRF into the nucleus and binding to the enhancer element B, which results in the activation of 2',5'-oligoadenylate synthetase gene expression.

Distinct positive and negative elements control the limited hepatocyte and choroid plexus expression of transthyretin in transgenic mice

Transthyretin (TTR) is a thyroid hormone transport protein that is secreted by hepatocytes into the serum and by the choroid plexus epithelium into the cerebral spinal fluid. The protein is not made elsewhere in adult animals in significant amounts. We find that the start site for mRNA synthesis is the same in both cell types. The sequences required for mouse TTR expression in cultured hepatocytes include an enhancer at -1.86 to -1.96 kbp and a promoter-proximal region at -70 to -200 bp relative to the mRNA cap site. We demonstrate that in transgenic mice these regulatory regions (approximately 300 bp) are sufficient for quantitatively normal expression of a TTR minigene in hepatocytes, but not for restricted expression in the choroid plexus cells of the brain. Instead, they direct aberrant widespread expression in regions of the brain outside the choroid plexus. With 3 kbp of upstream sequence the TTR minigene is expressed specifically in the choroid plexus as well as in the liver, demonstrating the normal cell type specificity for TTR. These results suggest that 3 kbp of upstream sequence contains positive element(s) required for choroid plexus expression which are distinct from those utilized in the hepatocyte, and may also contain negative element(s) that function to suppress transcription in other brain cell types.

Summer camps for diabetic children in Beijing of China

The first summer camp for diabetic children was held in 1984 in Beijing. Since then we have held summer camp every year, the last summer camp was the fifth camp in 1988. The purpose of summer camps for diabetic children are to train the patients and increase the skills of diabetics self-control practice. The recreation activities are also important for their good communication and psychological adaptation. The campers of camps were 28-35 diabetic children, totally 154 participants consisting of 73 boys and 81 girls. Most of the children were 10-14 years old. The staffs include pediatricians, nurses and others. The ratio of campers with staffs were 2.7-3.2. The session of the camps were always of five days length. The characters of activities in camps were all the arrangements must be for diabetic children, included planning diet, insuring the urine sugar exam, insulin injection before each meal, and give some lectures for training the managed skills of diabetes, meanwhile the recreation programs and exercise were also a consisting portion of activations. The summer camps were beneficial for diabetic children. They learned many useful techniques of diabetes and their capacity of life adaptation were increased, and the self-confidence enhanced their future daily life.

Signal transduction pathways in the induction of 2',5'-oligoadenylate synthetase gene expression by interferon alpha/beta

Treatment of quiescent BALB/c mouse 3T3 cells with murine interferon alpha/beta (IFN-alpha/beta) (1000 units/ml) leads to the appearance at 4 hr of 1.7-kilobase 2',5'-oligoadenylate (2',5'-OAS)mRNA as detected by Northern blot analysis. This mRNA accumulates for at least 18 hr. Two protein kinase C activators, 1,2-dioctanoyl glycerol and phorbol 12-myristate 13-acetate, suppress, whereas the calcium ionophore ionomycin enhances, the IFN-alpha/beta-induced expression of 2',5'-OAS mRNA. The 8-bromo and dibutyryl analogs of cAMP and the adenylate cyclase activator forskolin did not affect the induction of 2',5'-OAS mRNA by IFN-alpha/beta. In the absence of IFN-alpha/beta, the above agents used either singly or in combinations, did not induce 2',5'-OAS mRNA expression nor did platelet-derived growth factor (1-2 units/ml), fibroblast growth factor (6-100 ng/ml), or bovine serum (10-20%). Bovine serum also did not affect 2',5'-OAS mRNA induction by IFN-alpha/beta. The poly(ADP)-ribose synthetase inhibitor 3-aminobenzamide suppressed IFN-alpha/beta-induced 2',5'-OAS gene expression. These results suggest that in quiescent BALB/c 3T3 cells (i) the 2',5'-OAS gene is not responsive to the three major signal transduction pathways activated by diacylglycerol, Ca2+, and cAMP; (ii) induction of the 2',5'-OAS gene by IFN-alpha/beta is decreased by activation of the protein kinase C pathway but enhanced by elevation of intracellular [Ca2+].

Purification and characterization of nicotinamide deamidase from yeast

Nicotinamide deamidase (YNDase) has been purified from yeast through the use of a six-step procedure that includes molecular-sieve high performance liquid chromatography. The final preparation was homogeneous by the criteria of sodium dodecyl sulfate-gel electrophoresis, and the enzyme specific activity was determined to be 175 mumol of nicotinate formed per min/mg enzyme. Gel electrophoresis and molecular-sieve high performance liquid chromatography were employed also to characterize YNDase as a monomeric protein with a molecular weight of 34,000. A Km value for nicotinamide of 33 microM was determined for the deamidase activity at pH 6, and a pH range for optimal stability of 6-8.5 was established for this enzyme. The YNDase activity was also examined over a pH range at several substrate concentrations and both the log Vmax and log Vmax/Km plots versus pH suggested that a protonated amino acid residue with an apparent pKb value of 7.8 was essential to this activity. During an in vitro assay of the YNDase-catalyzed formation of nicotinate, ammonia was generated and detected chemically. Inhibition of the YNDase activity by nicotinaldehyde suggested the presence of either an essential lysine (Schiff's base formation) or cysteine residue (thiohemiacetal intermediate) at the YNDase active site. The relatively large value of the nicotinaldehyde inhibition constant (Ki = 68 microM), the observation that this analogue is a noncompetitive inhibitor of nicotinate formation, and the fact that this inhibition can be rendered irreversible through incubation with sodium borohydride, indicates that a Schiff's base intermediate is more likely to occur upon incubation of YNDase with nicotinaldehyde. However, YNDase is inactivated completely and irreversibly by N-ethylmaleimide at pH 6, and the enzyme is protected against this modification by either nicotinamide or nicotinate. These results suggest that both nicotinate and nicotinamide bind to YNDase, even though the enzymatic reaction is essentially irreversible, and that a cysteine residue may be present at the YNDase active site.

Characterization of fatty acid synthetase cDNA clone and its mRNA

Four cDNA clones have been identified by hybrid-select translation to contain the sequences complementary to fatty acid synthetase mRNA. The restriction mapping of these clones indicated that three of these, pFAS-7, pFAS-17 and pFAS-18, have sequences in common, and a fourth, pFAS-15, did not hybridize with the others, suggesting sequence to another region of the mRNA. Northern analysis of cytoplasmic poly(A) +RNA showed the presence of two bands at 9.2 Kb and 8.4 Kb. Similar analysis of nuclear RNA also showed the presence of two bands at 14 and 11 Kb. These probably represent unprocessed transcripts. Southern analysis of genomic DNA digested with EcoRI, BamHI, HindIII and PstI indicate the presence of a single gene copy for fatty acid synthetase.

Enzymatic assay procedures that employ high-performance liquid chromatography: competition between phosphoribosyltransferases for a common substrate

A survey of the phosphoribosyltransferase (PRTase) activities in yeast has been accomplished using reversed-phase high-performance liquid chromatographic assay procedures. The following bases were observed to be utilized during phosphoribosyl pyrophosphate (PRibPP)-dependent nucleotide syntheses: adenine, xanthine, hypoxanthine, guanine, uracil, orotate, nicotinamide, nicotinate and quinolinate. Gradient elution procedures have also been perfected that allow the separation of the two following sets of PRTase assay components: (1) adenosine monophosphate, nicotinate mononucleotide, orotate, adenosine triphosphate, nicotinate, adenosine diphosphate, inosine monophosphate and hypoxanthine, and (2) nicotinate mononucleotide, nicotinamide mononucleotide, adenosine triphosphate, nicotinate, adenosine diphosphate and nicotinamide. Separation 1 has been employed to examine the PRibPP allocation among the hypoxanthine PRTase, orotate PRTase and nicotinate PRTase catalyzed reactions, whereas separation 2 has been employed to define the role that ATP plays in the nicotinamide PRTase-catalyzed reaction along with the allocation of nicotinamide between the reactions catalyzed by nicotinamide PRTase and nicotinamide deamidase.

Cloning of DNA complementary to rat liver fatty acid synthetase mRNA

Clones, containing DNA complementary (cDNA) to rat liver fatty acid synthetase mRNA, were constructed and identified. cDNA of these clones was then used as a probe to quantify mRNA. The cDNA was synthesized to partially purified rat liver fatty acid synthetase mRNA. Double-stranded cDNA was then prepared and inserted into the PstI site of pBR322 using oligo(dG) X oligo(dC) tailing. Initial selection of the clones was by differential colony hybridization employing [32P]cDNA synthesized from poly(A)-rich mRNA, enriched and non-enriched in fatty acid synthetase mRNA, as probes. Plasmids, containing specific sequences complementary to the fatty acid synthetase mRNA, were identified by hybrid-arrest translation. Cloned cDNA inserts ranged from 300 to 1400 base pairs. Cloned cDNA was employed to probe for mRNA in hybridizations via the dot-blot method. These studies demonstrated an increase in fatty acid synthetase mRNA during dietary induction, which suggests that regulation may involve changes in transcription or changes in post-transcriptional processing of the mRNA.