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PubMed1977

Genetics of ribosomal protein methylation in Escherichia coli. I. A mutant deficient in methylation of protein L11.

Several thousand mutagenized clones of Escherichia coli were screened for methyl group incorporation into protein in crude extracts, in order to isolate mutants lacking the full complement of methyl groups in ribosomal proteins. One mutant isolated by this method and designated prm-1 incorporated 6-7 methyl groups per ribosome upon incubation of its ribosomes with a partially purified enzyme preparation from E. coli wild-type. The methyl groups were located exclusively in the 50S particle and for the most part (85%) in protein L11. Three methylated amino acids were detected: epsilon-N-trimethyllysine, epsilon-N-monomethyllysine, and an uncharacterized amino acid. These accounted respectively for 4.6, 1.3 and 0.9 methyl groups per ribosome. These results indicate that protein L11 in wild-type contains a stoichiometric amount of these methylated amino acids which are absent in mutant prm-1. Since this mutant is fully viable, its methylation deficiency does not result in a major defect in ribosome assembly or functioning.

Amino Acids↗
PubMed2018

Quantitation of DNA Methylation by Quantitative Multiplex Methylation-Specific PCR (QM-MSP) Assay.

The defining feature of the Quantitative Multiplex Methylation-Specific PCR (QM-MSP) method to sensitively quantify DNA methylation is the two-step PCR approach for a multiplexed analysis of a panel of up to 12 genes in clinical samples with minimal quantities of DNA. In the first step, for up to 12 genes tested, one pair of gene-specific primers (forward and reverse) amplifies the methylated and unmethylated copies of the same gene simultaneously and in multiplex, in one PCR reaction. This methylation-independent amplification step produces amplicons of up to 109 copies per μL after 36 cycles of PCR. In the second step, the amplicons of the first reaction (STEP 1) are quantified with a standard curve using real-time PCR and two independent fluorophores to detect methylated/unmethylated DNA of each gene in the same well (e.g., 6FAM and VIC). One methylated copy is detectable in 100,000 reference gene copies. Methylation is reported on a continuous scale. For the gene panel, the highest level of normal DNA methylation above which a sample would be called positive is derived by using Receiver Operating Characteristic (ROC), maximizing assay specificity and sensitivity to distinguish between normal/benign versus tumor DNA. QM-MSP can be applied to clinical samples of fresh or fixed ductal cells, ductal fluid, nipple fluid, fine needle aspirates, core biopsies, and tumor tissue sections.

Breast Neoplasms↗
PubMed1976

Induction of abortion by vaginal administration of 15(s)15-methyl prostaglandin F2alpha methyl ester. A comparison of two delivery systems.

15-methyl PGF2alpha methyl ester in a slow releasing vaginal device was administered to 30 women in the first and second trimester of gestation. Ten women were early pregnant (31-49 days following the last menstrual period) and the remaining 20 patients in the 10th to 20th week of gestation. The first group received either a device containing 10 mg 0.5% 15-methyl PGF2alpha methyl ester or a half of that device and the second group either a 0.5% or 1% device. The results were compared with those found following repeated vaginal administration of triglycerides suppositories, containing 15-methyl PGF2alpha methyl ester, to 50 early pregnant patients and 30 patients in the second trimester of gestation. The mean total dose of the compound given to these two groups was 3.9 and 7.8 mg respectively. All the 60 early pregnant patients aborted following treatment judged from clinical course and decreasing HCG values. Bleeding started as a rule three to six hours following the start of treatment and continued for 10 to 14 days. In two patients the abortion was incomplete. The side effects in the patients who received half the 0.5% device was comparable to those following the repeated vaginal suppositories while in the patients who obtained the whole 0.5% device, the frequency of side effects was increased indicating that an unnecessary high dose was given. In all the three groups of patients in the late first and second trimester of pregnancy, treatment resulted in abortion within 24 hours in 90% of the patients. In the 1% device an accumulation of side effects was found during the first hours following the start of treatment probably due to an initial, more rapid absorption of 15-methyl PGF2alpha methyl ester. With the repeated administration and with the 0.5% device, the side effects occurred mainly in the hours prior to abortion. However, in all three groups of patients the side effects were within acceptable levels. These preliminary results indicate that further development on the device may result in an effective one vaginal administration treatment for termination of both first and second trimester pregnancies.

Abortion, Induced↗
PubMed1979

Effect of a single treatment with the alkylating carcinogens dimethylnitrosamine and methyl methanesulphonate on liver regenerating after partial hepatectomy. IV. Effect on methylase-mediated methylation of DNA.

The possibility that carcinogens may affect methylase-mediated methylation of replicating DNA was investigated. A system eminently suitable for this purpose is liver regenerating after partial hepatectomy, as one injection of dimethylnitrosamine (DMN) given during the ensuing period of increased DNA synthesis induces hepatocellular carcinoma. Methylation of DNA by DNA methylase normally occurs only in proportion to DNA synthesis. Therefore simultaneous measurements were made of synthesis (incorporation of [14C]adenine into DNA adenine, or of d[5-3H]cytidine into DNA cytosine), and of methylation (incorporation of [methyl-3H]methionine into 5-methylcytosine of DNA) in liver regenerating after partial hepatectomy. After treatment with DMN, the ratio of methylation: synthesis remained within the normal range. Methyl methanesulphonate (MMS), a compound which damages DNA in regenerating liver in a similar but not identical way to DMN and which does not induce tumors in liver even when given after partial hepatectomy, caused an increase in methylation in relation to synthesis. These experiments therefore do not support the view that altered DNA methylase activity is involved in carcinogenesis.

Animals↗
PubMed1979

DNA methylation: organ specific variations in the methylation pattern within and around ovalbumin and other chicken genes.

The restriction enzymes HhaI and HpaII, whose activity is inhibited by cytosine methylation within their recognition sites, have been utilised as probes to study methylation in the vicinity of the ovalbumin gene in DNA from various chicken tissues. This was complemented by a preliminary study of methylation in the regions of chicken ovotransferrin (conalbumin), ovomucoid and beta-globin genes. From our data we conclude that HaI or HpaII sites can be divided in 3 classes according to their pattern of methylation in different tissues. In the first class of sites (mV class) the extent of methylation varies in different tissues. The patterns obtained show that methylation at the sites located within and around the 3 genes which code for egg white proteins is in general lowest in oviduct of laying hen, where these genes are expressed. However some sites are not methylated (m- class) and others are 95 to 100% resistant (m+ class) to digestion by HhaI or HpaII in the DNAs of all the tissues which were tested. Our study has also revealed a remarkable number of allelic variants for the presence of HhaI or HpaII sites in the region of the ovalbumin gene.

Animals↗
PubMed1976

Inhibition of rat liver RNA polymerases by action of the methylating agents dimethylnitrosamine in vivo and methyl methanesulfonate in vitro.

Dimethylnitrosamine maximally inhibits rat liver nuclear RNA synthesis by 50% at a dose of 40 mg/kg of body weight. The inhibition develops during the first 4 hr and persists through the 12th hr. All parenchymal cells of the lever lobule seem to be affected. The decreased RNA synthesis can be accounted for entirely by an inhibition of the RNA polymerase activities quantitatively solubilized and partially purified. A similar inhibition of the polymerase activities was demonstrated in the intact nuclei by inactivating the endogenous template with actinomycin D and assaying the polymerases with an added exogenous template, poly(deoxy-adenylate-deoxythymidylate). Chromatin was prepared by two methods differing in the extent to which they remove the endogenous polymerase activity. Each preparation was transcribed with either added Escherichia coli or partially purified rat liver nucleoplasmic RNA polymerase. With either polymerase or chromatin preparation, no inhibition of the template activity of liver nuclear chromatin isolated from the DMN-treated animals was detected. A similar mechanism of inhibition of RNA synthesis was produced by the action of the methylating agent methyl methanesulfonate on whole nuclei in vitro. The dose-dependent inhibition of RNA synthesis could be accounted for by an inhibition of the RNA polymerase activities quantitatively solubilized and partially purified from the affected nuclei. Chromatin prepared from the methyl methanesulfonate-treated nuclei had a normal template capacity with either E. coli or rat liver nucleoplasmic RNA polymerase. No preferential methylation of the RNA polymerases by [14C]methyl methanesulfonate could be demonstrated. It is concluded that the action of the two methylating agents on RNA metabolism is similar and that the inhibition of liver nuclear RNA synthesis results from inactivation of the RNA polymerases. At the same time, dimethylnitrosamine and methyl methanesulfonate leave the chromatin template intact, at least quantitatively, for the synthesis of RNA. The implications of such an effect on RNA synthesis are discussed.

Animals↗
PubMedDate not supplied

[Methylation of prokaryotic RNA by S-methyl methionine in in vivo experiments].

While cultivating the E. coli 113-3 strain on the mineral medium containing S-methyl-(methyl-3H)-methionine, the incorporation of methyl groups into 4S, 16S and 23S RNA proved to be over 5 times more effective as compared with the control, when L-(methyl-3H)-methionine acted as a donor of methyl groups. The ratio of methylated components has much in common and significant differences. All the types of RNA of E. coli grown in the mineral medium containing S-methyl methionine showed an increased ratio of m2G as compared with the corresponding types of RNA of E. coli after its cultivation in the methionine containing mineral medium.

Escherichia coli↗
PubMed1977

Effect of 15(s)15-methyl-PGF2alpha-methyl ester vaginal suppositories on circulating hormone levels in early pregnancy.

Intravaginal administration of 15-methyl-PGF2alpha-methyl ester in the form of suppositories terminated pregnancy in 70 percent of the cases whose last menstrual periods ranged from 35 to 56 days. The use of these suppositories in 49 patients, between 57 to 80 days of gestation, dilated the cervix by 10 mm or more, in one hundred percent of the cases. A decrease in circulating levels of estradiol-17beta and progesterone was observed following 15-methyl-PGF2alpha administration. The mean estradiol-17beta levels declined by about 55.9 percent at 9 hours whereas, the corresponding fall in progesterone was 32.7 percent. This was indicative of a direct action of 15-methyl-PGF2alpha on the corpus luteum. The vaginal use of 15-methyl-PGF2-alpha-methyl ester suppositories thus appears to be a promising method for the termination of early pregnancy and for pre-operative cervical dilatation. The termination of early pregnancy appears to be partly due to the luteolytic effect of 15-methyl-PGF2alpha besides stimulating uterine contractions.

Abortion, Induced↗
PubMed1976

Use of methyl iodide for probing the polarity of the immediate environment of --SH groups in thiolenzymes. Reaction of methyl iodide with thiosubtilisin.

A new approach is proposed for probing the polarity of the immediate environment of -SH groups in thiolenzymes, based on the alkylation of the -SH group with methyl iodide, a relatively small and non-polar molecule. Rate and activation parameters (delta H*, delta S*) for the reaction of the enzyme are compared to those of glutathione, a simple -SH compound alkylated in aqueous medium. The enzyme and model compound are also reacted with iodoacetamide, a polar counterpart of the non-polar methyl iodide. The above method was applied to thiolsubtilisin, an artificial thiolenzyme. 1. The ratio of the rates of alkylation of thiolsubtilisin and glutathione is about 20 times as high with methyl iodide as with iodoacetamide. 2. delta H* and delta S* for enzyme alkylation, as compared to those for glutathione, are remarkably lower with methyl iodide whereas they are slightly higher with iodoacetamide. 3. delta H* and delta S* for alkylation of thiolsubtilisin with methyl iodide are similar to those found with glutathione in 40% dioxane/water mixture. 4. The activation enthalpy and entropy values for the reaction of thiolsubtilisin with D-2-bromo-n-valeramide are lower than those for glutathione reaction. Consequently, in this respect, D-2-bromo-n-valeramide is similar to methyl iodide rather than to iodoacetamide. It is concluded that the -SH group of thiolsubtilisin is located in an environment less polar than water. The concentration of methyl iodide in this non-polar layer is higher than in the bulk solution, which results in an enhanced reaction rate.

Alkylation↗
PubMed1977

[Isolation and structure determination of the metabolites of 2-(1,3-dimethyl-xanthinyl-(7)-methyl)-4-methyl-morpholine--a xantinol derivative--from rat urine (author's transl)].

In the urine of rats the following metabolites of the xantinol derivative 2-(1,3-dimethyl-xanthinyl-(7)-methyl)-4-methyl-morpholine were found: 2-[1,3-dimethyl-xanthinyl-(7)-methyl]-morpholine and 2-[1,3-dimethyl-xanthinyl-(7)-methyl]-4-methyl-morpholin-5-one. These compounds represent about 13.7% of the p.o. applied 2-[1,3-dimethyl-xanthinyl-(7)-methyl]-4-methyl-morpholine. Their structure has been elucidated by IR-, PMR- and mass spectrometry.

Animals↗
PubMed2020

Harsh Parenting Predicts Novel HPA Receptor Gene Methylation and NR3C1 Methylation Predicts Cortisol Daily Slope in Middle Childhood.

Adverse experiences in childhood are associated with altered hypothalamic-pituitary-adrenal (HPA) axis function and negative health outcomes throughout life. It is now commonly accepted that abuse and neglect can alter epigenetic regulation of HPA genes. Accumulated evidence suggests harsh parenting practices such as spanking are also strong predictors of negative health outcomes. We predicted harsh parenting at 2.5&#xa0;years old would predict HPA gene DNA methylation similarly to abuse and neglect, and cortisol output at 8.5&#xa0;years old. Saliva samples were collected three times a day across 3 days to estimate cortisol diurnal slopes. Methylation was quantified using the Illumina Infinium MethylationEPIC array BeadChip (850&#xa0;K) with DNA collected from buccal cells. We used principal components analysis to compute a summary statistic for CpG sites across candidate genes. The first and second components were used as outcome variables in mixed linear regression analyses with harsh parenting as a predictor variable. We found harsh parenting significantly predicted methylation of several HPA axis genes, including novel gene associations with AVPRB1, CRHR1, CRHR2, and MC2R (FDR corrected p&#x2009;<&#x2009;0.05). Further, we found NR3C1 methylation predicted a steeper diurnal cortisol slope. Our results extend the current literature by demonstrating harsh parenting may influence DNA methylation similarly to more extreme early life experiences such as abuse and neglect. Further, we show NR3C1 methylation is associated with diurnal HPA function. Elucidating the molecular consequences of harsh parenting on health can inform best parenting practices and provide potential treatment targets for common complex disorders.

Child↗
PubMed1978

Identification of the methylated ribosomal proteins in HeLa cells and the fluctuation of methylation during the cell cycle.

Methylated proteins from HeLa cell cytoplasmic ribosomes have been identified. At least seven proteins are methylated and four of them are mildly acidic. The nature of the methylated amino acid in each protein is presented. In synchronized HeLa cell culture, the extent of methylation for both subunits varies with the cell cycle. Methylation of the 40 S subunit occurs heavily in the late G1 phase whereas methylation of the 60 S subunit is most pronounced in the early S phase.

Arginine↗
PubMed1976

Identification of the methyl phosphotriester of thymidylyl (3',5')thymidine as a product from reaction of DNA with the carcinogen N-methyl-N-nitrosourea.

The methyl phosphotriester of thymidylyl(3'-5')thymidine, Tp(Me)T, was obtained as a product of enzymic digestion of N-[14C]methyl-N-nitrosourea-methylated DNA or of N-methyl-N-nitrosourea-methylated [14C]thymine-labelled DNA. The identity of the 14C-labelled Tp(Me)T products was shown by co-chromatography of the 14C-labelled enzymic digests with synthetic Tp(Me)T on Dowex 50 (NH4+ form, eluted at pH 8), and by co-chromatography, on silica gel in 3 solvent systems, of the Tp(Me)T-containing fractions from the Dowex 50 column. This identity was confirmed by showing that the 14C-labelled DNA-derived products hydrolysed in 0.1 M sodium hydroxide at 37 degrees C at a rate identical with that of synthetic Tp(Me)T, and gave the four expected UV-absorbing products (thymidine, thymidylyl(3'-5')thymidine, and the methyl esters of 3'- and 5'-TMP) in the same ratios as the authentic triester.

Binding Sites↗
PubMed2026

Methylation histology reveals the molecular mechanism by which red light-mediated DNA methylation delays leaf senescence in pak choi (Brassica rapa subsp. chinensis).

Leaf senescence is a key factor affecting the postharvest quality and shelf life of vegetables. The specific mechanisms by which light environment and DNA methylation mediate leaf senescence remain unclear. This study explored the molecular mechanism by which red light (RL) LED delays leaf senescence through DNA methylation in pak choi (Brassica rapa subsp. chinensis). In this study, RL treatment significantly suppressed leaf senescence in pak choi during postharvest storage and downregulated the expression of senescence-associated genes (SAGs). Experiments with methylation inhibitors confirmed its association with DNA methylation. Furthermore, whole-genome bisulfite sequencing revealed that during storage-induced senescence, pak choi exhibited significantly reduced methylation levels across its genome, particularly in promoter regions, and RL treatment reversed this effect. Furthermore, virus-induced gene silencing and overexpression experiments confirmed the central role of the demethylase BrDML3 (BraA01g004250.3.5C) in this process. Subsequently, a transcription factor under its regulation, BrNAC55 (BraA05g032630.3.5C), was identified and shown to promote leaf senescence by activating downstream SAGs (BrSGR1, BrPPH, BrSAUR36) to promote leaf senescence. In addition, this study found that BrNAC55 can also form a feedback loop with BrDML3, continuously amplifying leaf senescence. This study elucidates the mechanism by which RL-mediated DNA methylation delays leaf senescence, providing a foundation for postharvest preservation technologies.

DNA Methylation↗
PubMed1979

Studies on bacterial chemotaxis. II. Effect of cheB and cheZ mutations on the methylation of methyl-accepting chemotaxis protein of Escherichia coli.

Radioactive proteins from chemotactic mutants of Escherichia coli with continuous tumbling phenotype (cheB and cheZ) and their otherwise isogenic parent were compared by two-dimensional gel electrophoresis. The system was capable of separating non-methylated methyl-accepting chemotaxis protein (MCP) from its methylated equivalent. The analysis of proteins from the envelope fraction of the bacteria showed that the cheB mutants contained a larger portion of methylated MCP than did the parent. However, the change of MCP methylation level was small, if any, in cheZ strains. The results suggest that the product of cheB gene and the product of cheZ gene are not functional complementary. The product of cheB gene functions in controlling the level of methylation at the stationary state of the organisms. In addition to known MCP species, a new MCP of about 43,000 daltons was found. This MCP appears to be involved in transducing signals of some sugars.

Bacterial Proteins↗
PubMed1977

Blood compatibility of methyl, methyl vinyl, methyl phenyl, and trifluoropropylmethylvinyl silicone rubber without silica fillers in the spiral-coiled membrane lung.

Spiral-coiled membrane lungs of 0.6 m2 surface area were fabricated from silicone rubber membranes coated with four types of commercially available pure-gum polysiloxane rubber: 1) polytrifluoropropylmethylvinylsiloxane, 2) polymethylphenylsiloxane, 3) polymethylvinylsiloxane, and 4) polydimethylsiloxane. Membranes lungs were tested in an arteriovenous shunt without added heparin after bypass was begun. All group 4 had major rise in resistance to blood flow or clotting in over 33% of the membrane lungs studied, after 6 hr of bypass. Membrane lungs with polydimethylsiloxane (group 4) had no rise in resistance to blood flow during 24 hr of bypass and had the least amount of changes in blood platelet count.

Animals↗