RNA and histone metabolism in small lymphocytes stimulated by phytohaemagglutinin

Phytohemagglutinin stimulation of lymphocytes improves mutation analysis of carbamoylphosphate synthetase 1

Carbamoylphosphate synthetase 1 (CPS1) is the first enzyme of the urea cycle. CPS1 deficiency is a rare autosomal-recessively inherited disorder that can lead to life-threatening hyperammonemia. Since there is no reliable biochemical marker for this disease, diagnosis relies on molecular means which is often done by RNA-based mutation analysis. Skin fibroblasts have been frequently used as a source of RNA while peripheral blood cells do not yield sufficient amounts of specific RNA. To avoid the costly and laborious use of cultured fibroblasts, we tried to use stimulated lymphocytes as an alternative. This was effectively achieved by short-term culture of full heparin blood in the presence of phytohemagglutinin. Hereby, subsequent reverse transcriptase-PCR of the CPS1 transcript became feasible and allowed to detect 16 different mutations (10 missense, 3 deletions, 2 nonsense, 1 duplication; 7 novel mutations) in 14 consecutive patients with CPS1 deficiency. When compared to retrospective data on cultured fibroblasts, the adapted method allowed substantial shortening of the median time to diagnosis (24 days versus 122 days, respectively). Besides disease causing mutations, we detected CPS1 transcript variants including one cryptic exon in RNA from lymphocytes with higher frequency than in RNA from fibroblasts. This underlines that all mutations found in RNA need to be confirmed by DNA sequencing. In conclusion, the presented approach improves the diagnostics of CPS1 deficiency. Besides the shortened time to diagnosis, the method is of particular importance for confirmation of findings of next generation sequencing and gene chips.

In vivo stimulation of nerve cells by phytohemagglutinin. II. Alterations in the rate of total and mRNA synthesis in the brain cortex of old rats

Bacto-phytohemagglutinin-P (PHA-P) was administered in form of a single intralumbar injection of 2 mg/100 g body weight dose to 24- to 28-mth-old female CGY rats. The accuracy of the injection technique was checked by adding 2% lidocaine to the injection mixture, which resulted in a transient and symmetric paralysis of the posterior limbs when reaching the cerebrospinal fluid. The total RNA content of the liver and brain cortex were measured, and phenolic extraction of RNA was performed the brain cortex. Poly(A) +RNA (mRNA) was separated from the total RNA of the brain cortex by oligo(dT)-cellulose chromatography. Pulse labeling with tritiated uridine was performed 45 min before killing the animals and the incorporation of the radiolabel was measured in the respective RNA classes and corrected for the nucleotide pool size. The rates of total and mRNA synthesis are expressed in percentages of the young untreated rats and compared to old untreated animals. The effects of PHA-P was studied at 4, 10, 20 and 44 h after its injection. A considerable increase of the total RNA content of the brain cortex was measured during the first 10 h of the experiment followed by a slow decrease. However, the RNA content of the brain cortex was still significantly higher at the end of experiment compared to untreated old rats. The rate of total RNA synthesis increased significantly during the first 10 h and remained constantly high until 44 h. The rate of mRNA synthesis increased to a higher extent than that of the total RNA, and also remained high until 44 h.

Regulation of pyruvate kinase expression and growth in mastocytoma cells. I. Initial observations

The specific activities of pyruvate kinase and phosphofructokinase but not lactate dehydrogenase increase as P-815 mastocytoma cells approach the stationary phase. During this growth period, the rates of uptake of labelled precursors into DNA, RNA and total protein decreases. On the other hand, the pyruvate kinase protein level changes in parallel with activity. Although the K-isozyme is the primary form of pyruvate kinase expressed, some M-type subunit is also present and both forms undergo an increase in specific activity. In addition, pyruvate kinase expression is also elevated by adding cAMP analogues with theophylline, butyrate or conditioned media. This increased level of expression is hypothesized to be a secondary event associated with a differentiation-like-induced expression of the mast cell phenotype.

Effect of malathion on nucleic acid synthesis in phytohemagglutinin-stimulated human lymphocytes

The effect of malathion, an organophosphorus insecticide, on DNA and RNA synthesis was investigated by measuring the rate of incorporation of 3H thymidine and 3H uridine, respectively, into human lymphocytes stimulated by phytohemagglutinin (PHA). Increasing concentrations of malathion, from 10 to 70 micrograms/ml, were added to human lymphocyte cultures at different times in relation to PHA introduction. The lowest applied dose of malathion (10 micrograms/ml) in most cases led to increased incorporation of both 3H thymidine and 3H uridine. Higher concentrations of malathion (30, 50, 70 micrograms/ml) caused a time- and dose-dependent decrease of radioisotope incorporation.

Chemical modification of nuclear proteins by erythropoietin

The spleen of the exhypoxic polycythemic mouse was employed as a model system to study the effect of erythropoietin on enzymes that chemically modify nuclear proteins. At selected time intervals after in vivo administration of erythropoietin, acetyltransferase and methyltransferase activity were measured in nuclei isolated from the spleens of treated mice. In addition, the incorporation of labeled methyl and acetate groups into individual histone proteins was also examined. A 36% increase in nuclear acetyltransferase activity was observed eight hours after administration of erythropoietin, whereas nuclear methyltransferase activity increased by 42% 24 hours after administration of the hormone. Selective acetylation or methylation of individual histone proteins was not observed, and it is concluded that activation of transcription by erythropoietin is not the result of acetylation or methylation of nuclear proteins.

Histone acetylation and hormone action. Early effects of aldosterone on histone acetylation in rat kidney

Histone acetylation in the kidney of the adrenalectomized rat was increased 5 min after a physiological dose of aldosterone. The increase was exclusively in the histone F2a1. The increase in histone acetylation was given by 9alpha-fluorocortisol, deoxycorticosterone and cortisol, but not by progesterone. The increase in histone acetylation was abolished by prior treatment of the animals with the anti-mineralocorticoid agent, SC14266 [potassium 3-(3-oxo-17beta-hydroxy-4,6-androstadien-17-yl) propionate]; the basal degree of histone acetylation was unaffected. Pretreatment of the animals with actinomycin D or cyclo-heximide did not affect the stimulation, showing the stimulation was not due to increased synthesis of enzyme.

Histone acetylation and hormone action. Early effects of oestradiol-17beta on histone acetylation in rat uterus

The effect of oestradiol treatment on the acetylation of histones of the immature rat uterus has been studied. A 10mug dose of oestradiol causes a 70% increase at 5min and a 140% increase at 10min after administration in the labelling of the histone fraction F2+F3. No effect of oestradiol is seen on the labelling of histones F1 or acidic non-histone chromatin proteins. The oestradiol stimulation is seen in animals pretreated with either cycloheximide or actinomycin D. The stimulation of labelling caused by oestradiol is completely abolished by pretreatment of the animals with the anti-oestrogen, nafoxidine. The stimulation is given by lower doses of oestradiol, by stilboestrol and oestriol, but is not given by testosterone. These results suggest that stimulation of histone acetylation in the uterus is the earliest known effect of the hormone on its target tissue.

[Studies of nucleic acids and protein metabolism during initiation of adventitious roots]

Changes in the metabolism of nucleic acids and proteins were followed during the initiation of adventitious roots of Cicer arietinum. During the first 24 h, several phases of activation of the metabolism were found. The use of inhibitors of RNA synthesis showed that an early phase of incorporation of precursors into RNA is essential for the initiation phenomena. This phase is more sensitive to inhibitors and activators (hormones) than all other phases. The rapid turn-over of RNA synthesized during the first 6 h and the inefficience of inhibitors after this time suggested that a stable (non-RNA) factor maintains the activation. This factor must be synthesized soon after the stimulus of cutting.