5-Bromouracil

less than 1 mg/mL at 75 °F (NTP, 1992)

In water, 815 mg/L, temp not specified

590 °F (NTP, 1992)

310 °C

5-bromouracil is a white powder. (NTP, 1992)

Solid; [Merck Index] White to off-white powder; [Acros Organics MSDS]

Warning

H302 (90.7%): Harmful if swallowed [Warning Acute toxicity, oral]

P264, P270, P301+P317, P330, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 43 reports by companies from 2 notifications to the ECHA C&L Inventory.

Causes somnolence, muscle weakness, and dyspnea in intraperitoneal lethal-dose studies of mice (LD50 = 1,400 mg/kg); [RTECS] May cause irritation; Harmful by ingestion; Risk of irreversible adverse health effects; [Acros Organics MSDS] See Uracil.

A halogenated amide. Organic amides/imides react with azo and diazo compounds to generate toxic gases. Flammable gases are formed by the reaction of organic amides/imides with strong reducing agents. Amides are very weak bases (weaker than water). Imides are less basic yet and in fact react with strong bases to form salts. That is, they can react as acids. Mixing amides with dehydrating agents such as P2O5 or SOCl2 generates the corresponding nitrile. The combustion of these compounds generates mixed oxides of nitrogen (NOx).

EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

SMALL SPILLS AND LEAKAGE: If you spill this chemical, you should dampen the solid spill material with water, then transfer the dampened material to a suitable container. Use absorbent paper dampened with water to pick up any remaining material. Seal your contaminated clothing and the absorbent paper in a vapor-tight plastic bag for eventual disposal. Wash all contaminated surfaces with a soap and water solution. Do not reenter the contaminated area until the Safety Officer (or other responsible person) has verified that the area has been properly cleaned.

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

EYES: irrigate opened eyes for several minutes under running water. INGESTION: do not induce vomiting. Rinse mouth with water (never give anything by mouth to an unconscious person). Seek immediate medical advice. SKIN: should be treated immediately by rinsing the affected parts in cold running water for at least 15 minutes, followed by thorough washing with soap and water. If necessary, the person should shower and change contaminated clothing and shoes, and then must seek medical attention. INHALATION: supply fresh air. If required provide artificial respiration.

The presence of 5-bromouracil (BU) as well as 5-bromo-2-deoxyuridine (BUdR) in the cultivation media of bacteria results in the distinct increase of UV sensitivity. With the nucleic acid base analogue 8-azaadenine (8-AA) a similar effect was confirmed, however, not so pronounced. In the experiments reported here the combined action of BU or BUdR and 8-AA on Escherichia coli, Proteus mirabilis, Bacillus subtilis and Bacillus cereus was investigated. The sensitization effect of BUdR does not increase if 8-AA is present additionally during cultivation. On the contrary, a decrease of sensibilization occurs. This result may be caused by the protective effect of the adenine derivative against UV irradiation, if it is present in the cell, but not incorporated into the DNA.

The damages induced in E. coli AB2487 recA by Cerenkov emission and ionizing radiation contribute in an additive fashion to the overall lethality, and do not interact in a synergistic fashion. Bromouracil substitution enhances the lethal action of high energy X-irradiation on E. coli AB2487 recA by a mechanism involving enhanced radiosensitivity and enhanced photosensitivity.

Thymidine phosphorylase, a pyrimidine salvage enzyme, transforms 5-bromouracil to 5-bromodeoxyuridine, a mutagenic analogue of thymidine. Ultimately, 5-bromouracil acts on DNA. It induces a random DNA point mutation via base substitution. The base pair will change from an A-T to a G-C or from a G-C to an A-T after a number of replication cycles, depending on whether 5-BrU is within the DNA molecule or is an incoming base when it is enolized or ionized. 5-Bromouracil normally pairs with adenine. However, the proportion of 5-bromouracil in the enol tautomer is higher than that of thymine because the bromine atom is more electronegative than is a methyl group on the C-5 atom. Thus, the incorporation of 5-bromouracil is especially likely to cause altered base-pairing in a subsequent round of DNA replication.

/LABORATORY ANIMALS: Developmental or Reproductive Toxicity/ ... the effect of dietary pyrimidine analogs on growth and survival of Drosophila melanogaster was determined. One pair of male and female, 8-hours-old, newly hatched, wild type Drosophila melanogaster adults were transferred to a vial containing food supplemented with thymine, 5-bromouracil, uracil, orotic acid, cytosine, or uridine monophosphate at 0.13% of diet. Flies grown without supplement served as controls. Flies were allowed to mate and lay eggs. One week later, the parental flies were removed, eggs were allowed to hatch and after metamorphosis through larval, and pupal stages at 25 degrees C. Newly hatched adults were counted. The number of adult flies that hatched on each supplemented diet compared with the number that hatched on the control diet was used to calculate toxicity. The pyrimidines used in this experiment were ranked as follows: thymine greater than 5-bromouracil greater than uracil greater than orotic acid greater than cytosine greater than uridine monophosphate in decreasing order of toxicity. Correlating pyrimidine structure with toxicity to wild type Drosophila melanogaster, the data suggest that the toxicity was associated with the presence of a methyl or bromide group attached to carbon #5 of the pyrimidine ring. The presence of a ribose-phosphate group at nitrogen #1 on the pyrimidine ring alleviated pyrimidine toxicity.

/ALTERNATIVE and IN VITRO TESTS/ Substitution of thymine with 5-bromouracil in DNA is known to change interaction between DNA and proteins, thereby inducing various biological phenomena. /The authors/ hypothesize that A/T-rich scaffold/nuclear matrix attachment region (S/MAR) sequences are involved in the effects of 5-bromodeoxyuridine. /They/ examined an interaction between DNA containing an intronic S/MAR sequence of the immunoglobulin heavy chain gene and nuclear halos prepared from HeLa cells. Upon substitution with 5-bromouracil, the S/MAR DNA bound more tightly to the nuclear halos. The multi-functional nuclear matrix protein YY1 was also found to bind more strongly to 5-bromouracil-substituted DNA containing its recognition motif. These results are consistent with the above hypothesis.

/ALTERNATIVE and IN VITRO TESTS/ The miscoding properties of a 5-bromodeoxyuridine (dB) containing DNA template during in vitro replication have been investigated. 5-bromodeoxyuridine was introduced site-specifically into the amber 16 codon of a 25-mer oligodeoxynucleotide representing part of the sequence of phi x174am16(+)DNA. The dB containing oligodeoxynucleotide served as a template for in vitro replication by DNA polymerase alpha, DNA polymerase I (Escherichia coli) and AMV reverse transcriptase. The amber 16 revertant assay was used to detect the presence of misincorporated bases in the replication products. For all three DNA polymerases, the presence of dB does not constitute a significant barrier to replication. Errors at the position of dB substitution were found to originate exclusively from dGTP:dB mispairing during in vitro replication thus inducing A-T----G-C transitions. The dGTP:dB mismatches are formed at a 2-4-fold higher frequency as compared to dGTP:T mismatches. Our results indicate that the miscoding potential of dB-substituted DNA templates during replication is only weak at the specific site observed.

/ALTERNATIVE and IN VITRO TESTS/ /The authors/ synthesized and studied by proton NMR a duplex heptaoligonucleotide containing a 5-bromouracil (brU)-adenine base pair. This represents the first structural characterization of a B-form DNA containing brU. The brU.A base pair is Watson-Crick rather than Hoogsteen as seen for the monomers in the crystalline state. From analysis of the NOESY spectra at very short mixing times evidence is presented that substitution of brU for T induces significant conformational changes from that of a normal B DNA. The helix twist between brU4.A11 and G3.C12 is ca. 15 degrees and for both brU4 and G3 the glycosyl torsion angles are significantly changed. The imino proton of the bru.A base pair shows a pH insensitive line with which shows that the pK of brU in this base pair is very much higher than that of the monomer.

For more Non-Human Toxicity Excerpts (Complete) data for BROMOURACIL (23 total), please visit the HSDB record page.

LD50 Mouse ip 1400 mg/kg

LD50 Rat ip 1700 mg/kg

/Among/ halogenated pyrimidines ... if one compares the van der Waals radii of the various 5-position substituents, the dimension of the fluorine atom resembles that of hydrogen /ie, uracil/, whereas the bromine and iodine atoms are larger and close in size to the methyl group /ie, thymine/ ... /Pyrimidine analogs/

Cultivation of E. coli cells in the presence of 5-bromodeoxyuridine (BUdR) leads to formation of lesions in the cellular DNA which affect its secondary structure, as reflected by changes in temperature profiles. Such DNA contains single-stranded regions susceptible to endonuclease S1. One of the major sources of the BU-induced lesions appears to be dehalogenation of incorporated 5-bromouracil (BU) residues, with accompanying formation of uracil. The presence of uracil residues in such DNA was demonstrated directly by chromatography of hydrolyzates, and by the susceptibility of such residues to uracil-DNA glycosylase. The number of uracil residues was dependent on the extent of damage in the DNA, and decreased during the DNA repair that accompanied reactivation of bromouracil-inactivated cells. Dehalogenation of incorporated BU presumably results in formation of apyrimidinic sites by uracil-DNA glycosylase, and then single-strand nicks either by AP-endonuclease and/or dehalogenation. The findings are relevant to the mechanism of BU-induced mutagenesis.

The early studies are recounted, that led to the discovery of the ubiquitous process of DNA excision repair, followed by a review of the pathways of transcription-coupled repair (TCR) and global genomic nucleotide excision repair (GGR). Repair replication of damaged DNA in UV-irradiated bacteria was discovered through the use of 5-bromouracil to density-label newly synthesized DNA. This assay was then used in human cells to validate the phenomenon of unscheduled DNA synthesis as a measure of excision repair and to elucidate the first example of a DNA repair disorder, xeroderma pigmentosum. Features of the TCR pathway (that is defective in Cockayne syndrome (CS)) include the possibility of "gratuitous TCR" at transcription pause sites in undamaged DNA. The GGR pathway is shown to be controlled through the SOS stress response in E. coli and through the activated product of the p53 tumor suppressor gene in human cells. These regulatory systems particularly affect the efficiency of repair of the predominant UV-induced photoproduct, the cyclobutane pyrimidine dimer, as well as that of chemical carcinogen adducts, such as benzo(a)pyrene diol-epoxide. Rodent cells (typically lacking the p53-controlled GGR pathway) and tumor virus infected human cells (in which p53 function is abrogated) are unable to carry out efficient GGR of some lesions. Therefore, caution should be exercised in the interpretation of results from such systems for risk assessment in genetic toxicology. ...

The incorporation of bromouracil into the deoxyribonucleic acid (DNA) of bacteria and viruses has been explained on the basis that bromouracil is similar to thymine in its ability to form hydrogen bonds with adenine. Enzymatic experiments support this interpretation. Bromouracil incorporation into DNA proceeds via bromouracil deoxynucleoside triphosphate, which is an effective substitute for thymine deoxynucleoside triphosphate in the replication of DNA. Results with this and other base analogues have shown that the enzymatic replication of DNA is governed by pairing of a 6-aminopyrimidine to a 6-ketopurine (e.g., cytosine to guanine) and of a 6-ketopyrimidine to a 6-aminopurine (e.g., thymine to adenine). Several questions might be raised about this generalization. First, the accuracy previously achieved in measuring in vitro incorporation disclosed deviations from this rule only when they occurred with a frequency greater than 0.02 per cent. Would a more sensitive technique reveal pairing errors occurring at an even lower frequency? Second, the incorporation of bromouracil into viral or bacterial DNA is associated with an increase in the mutation rate; mutations due to occasional pairing of guanine with tautomeric forms of thymine or bromouracil that resemble cytosine has been suggested by Watson and Crick and Freese. Matching of bromouracil with guanine instead of with adenine leads, in subsequent replications, to a G-C pair in place of an original A-T. Would the presence of bromouracil in a DNA primer increase the incidence of "incorporation errors" when the DNA is enzymatically replicated? Finally, Shapiro and Chargaff determined the yield of pyrimidine nucleotides and oligonucleotides after acid hydrolysis of bromouracil-substituted Escherichia coli DNA and concluded that the inclusion of bromouracil in DNA led to drastic changes in the over-all arrangement of the bases. It was therefore important to check this conclusion by another method, for example, by analysis of nearest-neighbor base sequences. The availability of a DNA-like polymer made up exclusively of A and T arranged in alternating sequence (dAT polymer)7 made possible the synthesis of the analogous dABU polymer. These polymers are ideal primers for studying the mismatched incorporation of G residues. Using an assay that would have revealed one G residue per 105 A and T nucleotides polymerized, /the authors/ failed to observe G incorporation in dAT-primed reactions. However, with dABU as primer, the incorporation of G was unequivocal; it occurred at frequencies ranging from 1 per 2,000 to 1 per 25,000 nucleotides polymerized. These "errors" induced by BU are 2 to 3 orders of magnitude too low in frequency to account for the nucleotide disarrangement reported by Shapiro and Chargaff. /The authors/ therefore determined the nucleotide sequences in bromouracil-substituted E. coli DNA by the nearest-neighbor analysis; arrangement of nucleotides was indistinguishable from that in the normal sample. Enzymatic replication of a DNA-like polymer which contains only adenine and thymine residues (dAT polymer) revealed no detectable incorporation of guanine residues. The level of sensitivity of these experiments shows the frequency of "aberrant" guanine incorporation to be less than one residue per 28,000-580,000 adenine and thymine nucleotides polymerized. In the replication of an analogous polymer containing bromouracil in place of thymine (dABU polymer), the incorporation of guanine was unequivocal. It occurred at a frequency of one per 2,000 to 25,000 adenine and thymine nucleotides polymerized. Analysis of the sequential arrangement of the incorporated guanine residues in the synthesized product showed the nearest neighboring base to be bromouracil, guanine, and adenine with frequencies of 41, 42, and 17%, respectively. Current theories /in 1962/ of bromouracil mutagenesis, if applied to the replication of this polymer, would have predicted the incorporation of guanine exclusively next to bromouracil. The nearest-neighbor nucleotide sequences of normal E. coli DNA were compared with those of bromouracil-substituted E. coli DNA and found to be indistinguishable (-42%). This analysis does not support a contention based on results from acid hydrolysis of DNA that drastic changes in sequence result from substitution of bromouracil in E. coli DNA.

... The radiosensitization properties of BrdUrd result primarily from the electrophilic nature of the bromine, making it a good leaving group and leading to the irreversible formation of the uridine-yl radical (dUrd(.)) or the uridine-yl anion (dUrd(-)) upon addition of an electron. The radiolytic loss of the bromine atom is greatly suppressed in double-stranded compared to single-stranded DNA. Thus /the authors/ propose that the radiosensitization effects of bromouracil in vivo will likely be limited to single-strand regions such as found in transcription bubbles, replication forks, DNA bulges and the loop region of telomeres. /The authors believe that their /results may have profound implications for the clinical use of bromodeoxyuridine (BrdUrd) as a radiosensitizer as well as for the development of targeted radiosensitizers.

Eosinophils use eosinophil peroxidase, hydrogen peroxide (H(2)O(2)), and bromide ion (Br(-)) to generate hypobromous acid (HOBr), a brominating intermediate. This potent oxidant may play a role in host defenses against invading parasites and eosinophil-mediated tissue damage. In this study, /the authors/ explore the possibility that HOBr generated by eosinophil peroxidase might oxidize nucleic acids. When /the authors/ exposed uracil, uridine, or deoxyuridine to reagent HOBr, each reaction mixture yielded a single major oxidation product that comigrated on reversed-phase HPLC with the corresponding authentic brominated pyrimidine. The eosinophil peroxidase-H(2)O(2)-Br(-) system also converted uracil into a single major oxidation product, and the yield was near-quantitative. Mass spectrometry, HPLC, UV--visible spectroscopy, and NMR spectroscopy identified the product as 5-bromouracil. Eosinophil peroxidase required H(2)O(2) and Br(-) to produce 5-bromouracil, implicating HOBr as an intermediate in the reaction. Primary and secondary bromamines also brominated uracil, suggesting that long-lived bromamines also might be physiologically relevant brominating intermediates. Human eosinophils used the eosinophil peroxidase-H(2)O(2)-Br(-) system to oxidize uracil. The product was identified as 5-bromouracil by mass spectrometry, HPLC, and UV--visible spectroscopy. Collectively, these results indicate that HOBr generated by eosinophil peroxidase oxidizes uracil to 5-bromouracil. Thymidine phosphorylase, a pyrimidine salvage enzyme, transforms 5-bromouracil to 5-bromodeoxyridine, a mutagenic analogue of thymidine. These findings raise the possibility that halogenated nucleobases generated by eosinophil peroxidase exert cytotoxic and mutagenic effects at eosinophil-rich sites of inflammation.

... Using a sensitive and specific mass spectrometric method, /the authors/ detected two products of myeloperoxidase, 5-chlorouracil and 5-bromouracil, in neutrophil-rich human inflammatory tissue. Myeloperoxidase is the most likely source of 5-chlorouracil in vivo because halogenated uracil is a specific product of the myeloperoxidase system in vitro. In contrast, previous studies have demonstrated that 5-bromouracil could be generated by either eosinophil peroxidase or myeloperoxidase, which preferentially brominates uracil at plasma concentrations of halide and under moderately acidic conditions. These observations indicate that the myeloperoxidase system promotes nucleobase halogenation in vivo. Because 5-chlorouracil and 5-bromouracil can be incorporated into nuclear DNA, and these thymine analogs are well known mutagens, our observations raise the possibility that halogenation reactions initiated by phagocytes provide one pathway for mutagenesis and cytotoxicity at sites of inflammation.

5-bromouracil is metabolized into 5-bromodeoxyuridine via thymidine phosphorylase. (L626)

Drugs that are chemically similar to naturally occurring metabolites, but differ enough to interfere with normal metabolic pathways. (From AMA Drug Evaluations Annual, 1994, p2033)

Chemical agents that increase the rate of genetic mutation by interfering with the function of nucleic acids. A clastogen is a specific mutagen that causes breaks in chromosomes.

Used as an experimental mutagen; Alters DNA base-pair sequences by replacing thymine; [Merck Index]

Brominated derivative of uracil that acts as an antimetabolite, substituting for thymine in DNA. It is used mainly as an experimental mutagen, but its deoxyriboside ( BROMODEOXYURIDINE) is used to treat neoplasms

Photochemical induced cross-links between protein and nucleic acids are useful tools in the study of the protein-DNA interactions. The substitution of thymine by 5-bromouracil in DNA increases the photocross-linking yield, and reduces the direct damage to both DNA and proteins. ...

Laboratory chemical used as a mutagen in many mutagenesis experiments.