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Rapid synthesis of oligodeoxyribonucleotides. V. Further studies in solid phase synthesis of oligodeoxyribonucleotides through phosphotriester intermediates.

The phosphotriester solid phase method of oligodeoxyribonucleotide synthesis on a polyamide support [M.J. Gait et al. (1980) Nucleic Acids Research 8, 1081-1096] has been applied to purine rich oligodeoxyribonucleotides of 10-12 units. Use of trichloroacetic acid as reagent for removal of terminal dimethoxytrityl groups reduced depurination during chain assembly. Improvements to reaction and isolation conditions for the preparation of monomer and dimer building blocks are also described. The new methods provide a simple, quick and efficient procedure for medium length oligodeoxyribonucleotide synthesis on a scale adequate for most requirements of molecular biology.

Base Sequence

Rapid synthesis of oligodeoxyribonucleotides. VII. Solid phase synthesis of oligodeoxyribonucleotides by a continuous flow phosphotriester method on a kieselguhr-polyamide support.

A new kieselguhr-polydimethylacrylamide support has been used in a continuous flow, column system for solid phase synthesis of oligodeoxyribonucleotides by a phosphotriester procedure. Using only protected mononucleotides a 14-mer, 20-mer and 27-mer were assembled in high repetitive yield using a simple manually operated, bench top apparatus.

Acrylamides

[Effective selective modification of a single-stranded fragment of DNA with alkylating derivatives of short oligodeoxyribonucleotides in the presence of reaction effectors N-(2-hydroxyethyl)phenazine derivatives of oligodeoxyribonucleotides].

Tri-, tetra-, penta- and hexanucleotides bearing a reactive 4-(N-methylamino-N-2-chloroethyl)benzylamide group can effectively and selectively modify a single-stranded DNA fragment (302 nucleotides) in the presence of effectors, N-(2-hydroxyethyl)phenazinium derivatives of oligonucleotides complementary to DNA sequences adjacent to the binding site of the reagent. The reagents investigated modify not only single-stranded but also secondary-structured DNA regions. The modification extent depends on the length of oligonucleotide parts of the reagent and effector. A gap between the two stretches associated with the target DNA prevents the effector from functioning. The substitution of an octanucleotide effector by two tetranucleotide ones only slightly reduces the modification extent with a hexanucleotide reagent. A very efficient and specific modification can be achieved by using two effectors flanking the reactive oligonucleotide derivative. The approach leads to the modification extent of up to 89% with a hexanucleotide reagent.

Alkylating Agents

Base sequence selectivity in the binding of 7(R),8(S)-dihydroxy-9(S),10(R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene to oligodeoxyribonucleotide duplexes.

The effect of nucleotide sequence on the binding of 7(R),8(S)-dihydroxy-9(S),10(R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BPDE] to the exocyclic amino group of deoxyguanosine was investigated in duplexes formed by self-complementary oligodeoxyribonucleotide decamers which contained two deoxyguanosines (dGs) within unique sequences. A 35S-postlabeling procedure was developed for analysis of (+)-anti-BPDE adducts as dinucleotides containing 5'-(+)-anti-BPDE-dG adducts. This allows identification of the 3' neighbor of the reacted guanine and permits quantitation of the binding of (+)-anti-BPDE to each specific guanine in the oligodeoxyribonucleotide duplexes. Of all the central dG-containing sequences studied, dG surrounded by deoxycytidines (CGC) reacted to the greatest extent: over 4-fold more (+)-anti-BPDE bound to this central dG compared to the least reactive deoxyguanosine (AGT). (+)-anti-BPDE exhibited a preference for binding to a central deoxyguanosine when either the 5' or 3' neighbor was deoxyguanosine. The binding of (+)-anti-BPDE to oligodeoxyribonucleotide duplexes containing different numbers of consecutive dGs was analyzed in order to determine how the length of these sequences influences binding. Increases in the length of consecutive deoxyguanosine residues from 3 to 5 had little effect on the quantity of (+)-anti-BPDE bound to dG above that expected from the presence of a neighboring dG and an increase in the number of dG residues available for reaction. The results obtained with these oligodeoxyribonucleotide duplexes were consistent with the data available for the reaction of (+)-anti-BPDE with DNA, indicating that these duplexes are a valuable model for studying the effect of base sequence on the interaction of BPDE isomers with DNA. The dinucleotide postlabeling technique developed for these studies, with appropriate oligodeoxyribonucleotides and chromatographic conditions, will be useful for determining the effect of base sequence on the binding of other hydrocarbon diol epoxides as well as other reactive hydrocarbon metabolites to deoxyguanosine or deoxyadenosine in oligodeoxyribonucleotide duplexes and fragments of DNA.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide

T4 RNA ligase catalyzed synthesis of base analogue-containing oligodeoxyribonucleotides and a characterization of their thermal stabilities.

Self-complementary oligodeoxyribonucleotides containing the base analogues 2-aminopurine, 2,6-diaminopurine, N6-methyladenine, uracil, and 5-bromouracil were synthesized by a general method that allows incorporation of the analogues at specific positions. The method uses chemically synthesized partial sequences but circumvents the need for protected base analogues by incorporating their unprotected 3',5'-bisphosphate derivatives enzymatically. T4 RNA ligase was used to add the analogues to the oligodeoxyribonucleotides with yields from 54 to greater than 95 percent. Oligodeoxyribonucleotides were joined to the oligodeoxyribonucleotides containing the analogues at their 3'-termini in yields from 22 to 81 percent. The high yields obtained in these joinings suggest that RNA ligase should be of general use for the specific incorporation of other deoxyribonucleotide analogues into oligodeoxyribonucleotides. The oligodeoxyribonucleotides containing the base analogues were characterized by their mobilities during HPLC, nucleoside compositions, sequences, and thermal stabilities.

Adenine

Synthetic oligodeoxyribonucleotides as tools in molecular genetics: the characterization of the CYC1 (iso-1-cytochrome c encoding) locus of Saccharomyces cerevisiae.

The use of synthetic oligodeoxyribonucleotides as tools for the isolation, characterization and mutagenesis of eukaryote genes has played a major role in the molecular definition of the CYC1 locus of Saccharomyces cerevisiae, which is the structural gene for the apoprotein of iso-1-cytochrome c. Thus, the possibility of using a synthetic oligodeoxyribonucleotide as a probe to identify and monitor the isolation of a specific gene was first established by model studies which defined the melting temperatures (TmS) for duplexes of oligonucleotides of different lengths and base compositions. This led to the isolation of the CYC1 locus using a synthetic 13 nucleotide probe. A more convenient strategy for determination of DNA sequences by the Sanger method was provided by using synthetic oligodeoxyribonucleotides as primers with denatured double-strand plasmid DNA as template. By this means, the sequence of the CYC1 locus was determined by "walking" along the gene without isolating restriction fragments of the DNA or separating DNA strands. Synthetic oligodeoxyribonucleotides, used as primers for reverse transcriptase with mRNA as template, were also used to precisely define the 5'- and 3'-ends of the iso-1-cytochrome c mRNA. Yet another application of synthetic oligodeoxyribonucleotides is their use as specific mutagens after in vitro incorporation into double-stranded DNA. In the case of iso-1-cytochrome c, this mutagenic strategy is being used to define the role of conserved amino-acids in cytochrome function.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromosome Mapping

Binding of complement by complexes between antibodies to nucleic acid constituents and short oligodeoxyribonucleotides.

Oligodeoxyribonucleotides act as inhibitors of the complement fixation caused by complexes between antibodies to defined oligodeoxyribonucleotides and denatured DNA. At concentrations higher than 50 micrograms oligodeoxyribonucleotide/ml complement fixation occurred in the absence of antigen. The extent of complement binding depends on the specificity of the antibodies as well as on the composition of the oligodeoxyribonucleotides. Complement fixation is observed most strongly with antisera to oligodeoxyribonucleotides and to denatured DNA, which belong predominantly to the IgM class. With two LE-sera, containing antibodies to denatured and to native DNA, no complement fixation was found. It is supposed that specific interactions of the oligodeoxyribonucleotides with amino acid residues closely neighbored to the antibody combining site lead to conformational changes in the antibody molecules and to an activation of the complement binding site.

Animals

An efficient method for the sequence analysis of oligodeoxyribonucleotides.

Modifications of the chemical method of DNA sequence analysis that permit rapid and reliable sequence determination of single-stranded oligodeoxyribonucleotides as short as 4 nucleotides in length are reported. The principal changes made were increasing the level of chemical modification and optimizing the conditions for recovery of the chemically modified oligodeoxyribonucleotides. This method includes two approaches to the removal of [gamma-32P]ATP from 32P-labeled oligodeoxyribonucleotides and is especially useful in the determination of the sequence of chemically synthesized oligodeoxyribonucleotides, which are generally between 4 and 20 nucleotides in length.

Animals

The use of synthetic oligodeoxyribonucleotides to produce specific deletions in the araBAD promoter of Escherichia coli B/r.

Two oligodeoxyribonucleotides were chemically synthesized and used to specifically mutate the regulatory region of the araBAD operon in Escherichia coli B/r. One oligodeoxyribonucleotide introduced a 3-bp deletion in the araC activator binding site, the other a 3-bp deletion in the CRP-cAMP binding site. The mutations were introduced onto an ara insert cloned in an M13 vector using the synthetic oligodeoxyribonucleotides as primers and the (+) strand of an M13 mp2::ara hybrid phage as a template in an in vitro polymerization reaction. Hybridizations using the original synthetic oligodeoxyribonucleotide as a radioactive probe identified phage containing the desired deletion. The mutant ara inserts were subcloned into a stable plasmid for functional analysis. Transcription studies performed on strains containing the mutant ara plasmids demonstrated that both mutations reduced the amount of araBA mRNA synthesized in the presence of L-arabinose.

Arabinose

Evidence that a triplex-forming oligodeoxyribonucleotide binds to the c-myc promoter in HeLa cells, thereby reducing c-myc mRNA levels.

A synthetic 27-base-long oligodeoxyribonucleotide, termed PU1, has been shown to bind to duplex DNA to form a triplex at a single site within the human c-myc P1 promoter. PU1 has been administered to HeLa cells in culture to examine the feasibility of influencing transcription of the c-myc gene in vivo. It is shown that uptake of PU1 into the nucleus of HeLa cells is efficient and that the compound remains intact for at least 4 hr. In nuclei extracted from PU1-treated cells, inhibition of DNase I cleavage is detected within the c-myc P1 promoter at the target site for triplex formation. The inhibition is shown to be both site and oligodeoxyribonucleotide specific. After cellular uptake of PU1, it is shown that steady-state mRNA arising from the c-myc P1 initiation site is selectively reduced relative to total mRNA, relative to mRNA from the alternative c-myc P2 initiation site, and relative to mRNA derived from the beta-actin promoter. Significant mRNA repression is not seen upon treating cells with oligodeoxyribonucleotides that fail to bind to the P1 promoter target. Taken together, these data suggest that triplex formation can occur between an exogenous oligodeoxyribonucleotide and duplex DNA in the nucleus of treated cells.

Base Sequence

The preparative synthesis of oligodeoxyribonucleotides using RNA ligase.

The synthesis of nmol quantities of defined sequences of oligodeoxyribonucleotides using T4 RNA ligase has been demonstrated. Reacting using from 18 to 200 nmol of substrates in which a single 2'-deoxyribonucleoside 3',5'-bisphosphate was added to an oligodeoxyribonucleotide resulted in yields from 13 to 95%. When two oligodeoxyribonucleotides were similarly joined using RNA ligase, the yields ranged from 10 to 50%. Although the reactions contained high concentrations of enzyme and were incubated from 5 to 21 days, there was little degradation of either substrates or products. We have also characterized an unusual product which arises when 3'-phosphate terminated oligodeoxyribonucleotides are incubated with RNA ligase and high concentrations of ATP. This product has an adenylyl group linked to the 3'-phosphate by an anhydride bond. The mechanistic and synthetic implications of forming this product are discussed.

Base Sequence

alpha-DNA. VI: Comparative study of alpha- and beta-anomeric oligodeoxyribonucleotides in hybridization to mRNA and in cell free translation inhibition.

alpha and beta-anomeric d(G2T12G2) oligodeoxyribonucleotides were compared for their hybridization to rA12: the observed melting temperatures are 27 degrees C for beta-oligodeoxyribonucleotide/RNA hybrid and 53 degrees C for alpha-oligodeoxyribonucleotide/RNA. alpha-oligonucleotides with the four bases, complementary to natural mRNAs, were synthesized for the first time, labeled at their 5'-end with [32P] and used as probes in Northern blot experiments. In spite of these higher affinities for their target RNA's, they were unable to block translation of natural or synthetic mRNA's in rabbit reticulocyte lysate. We have studied the RNase H activity on model rA12:alpha- or beta-d(G2T12G2) hybrids or on mRNA:alpha- or beta-oligonucleotides hybrids. Specific hybridization protects RNA strech when using alpha-oligonucleotides but not beta-oligonucleotides. Thus, our results show the inability of RNase H to degrade RNA in alpha-oligodeoxyribonucleotides:RNA duplexes.

Endoribonucleases

Hydration of single-stranded phosphodiester and phosphorothioate oligodeoxyribonucleotides.

Infrared spectroscopy was used to identify hydration-sensitive structural differences between single- stranded phosphorothioate (PS) and phosphodiester (PO) oligodeoxyribonucleotides. Spectra were recorded in the mid-infrared region, 500-1800 cm-1, at relative humidities between 0 and 98%; the PS and PO spectra are substantially different. The hydration effects on spectral bands in these single-stranded oligodeoxyribonucleotides is markedly different from such behavior in double- and triple-stranded oligodeoxyribonucleotides. A strong absorption occurs at 656 cm-1 in the phosphorothioate sample which is completely absent from the PO spectra. Gravimetric measurements were carried out on one PS and one PO sample to monitor and confirm hydration. The calculated BET adsorption constants [Brunauer, S., Emmett, RH. and Teller, E. (1938) J. Am. Chem. Soc., 60, 309-319] are 1.2 and 1.4 water molecules per nucleotide in the first hydration layer of PS and PO respectively. While the gravimetric data indicate that the single-stranded oligodeoxyribonucleotides hydrate very similarly to duplex DNA, the mid-infrared conformational marker bands are strikingly different from those observed for duplex DNA. In particular, the Vas of the phosphate group (PO2) at 1222 cm-1 in the single-stranded PO spectra is independent of relative humidity.

Base Sequence

A novel class of condensing reagents in phosphodiester oligodeoxyribonucleotides synthesis. Application of the constituents of free terminal carboxy oxytocine gene.

Benzotriazol-1-yl-oxy-tris (dimethylamino) phosphonium salts have been used as novel condensing agents to promote internucleotide bond formation in phosphotriester oligodeoxyribonucleotide synthesis. The effectiveness of these stable compounds has been shown by the synthesis of the six oligodeoxyribonucleotide building blocks of the carboxy terminal oxytocine gene. Some modifications incorporated in the phosphotriester method include a rapid procedure to prepare the fully protected dideoxyribonucleotide blocks and size exclusion chromatography of the deprotected oligodeoxyribonucleotides. The triester oligodeoxyribonucleotides were studied by chemical ionization mass spectrometry.

Base Sequence

A general method for the purification of synthetic oligodeoxyribonucleotides containing strong secondary structure by reversed-phase high-performance liquid chromatography on PRP-1 resin.

Synthetic 5'-dimethoxytritylated oligodeoxyribonucleotides, which contained strong secondary structure, were satisfactorily denatured and purified by reversed-phase HPLC on PRP-1 columns when strongly alkaline conditions (0.05 M NaOH) were employed. This procedure was suitable for the purification of hairpin structures, e.g., d(CG)nT4(CG)n (n = 4, 5, 6), and oligo(dG) sequences, e.g., d(G)24, as well as oligodeoxyribonucleotide probes which contained degenerate base sites. Oligodeoxyribonucleotides as long as 50 bases in length were purified. Recovery of injected oligonucleotides was typically 90% or better. The high capacity of the PRP-1 resin also allowed purification to be performed on a preparative scale (2-8 mg per injection). Enzymatic degradation and HPLC analysis indicated that no modification of the heterocyclic bases occurred under the alkaline conditions described.

Base Sequence

Techniques for using antisense oligodeoxyribonucleotides to study gene expression.

Molecular biology is providing powerful tools for cloning and sequencing genes. The more difficult task is that of ascribing functions to the specific DNA sequences that appear to code for proteins, the "open reading frames," or of regulating the expression of known genes in biological systems in order to determine their contributions to cellular functions. The classical genetic approach of making mutants is difficult in eukaryotic systems, with the exception of yeasts and viruses, and has proved of limited utility. A promising approach to this problem has been to introduce into either the in vitro assay or tissue culture system oligodeoxyribonucleotides with nucleotide sequences complementary to the protein coding or "sense" sequence, usually referred to as "antisense" oligonucleotides. The term MATAGEN (MAsking TApe for Gene ExpressioN) has also been used for these compounds, which appear to inhibit gene expression predominantly by hybridization arrest of translation. Interest in the use of antisense molecules for the study of gene expression and regulation has increased dramatically in the past few years. The demonstrated utility of the antisense oligomer in both in vitro and tissue culture assays, the increased availability of nucleotide sequence data as well as improvements in nucleic acid sequencing techniques, and the automation of synthetic procedures for their preparation have made studies using these molecules more practical. This review focuses on short oligodeoxyribonucleotides, which offer important stability and synthetic advantages over the use of antisense RNA transcripts, and is intended as an introduction to practical approaches in the use of antisense oligodeoxyribonucleotides in biological systems. For synthetic techniques, the reader is referred to the individual references cited.

Animals