Chemistry: molecular biology and microbiology – Enzyme – proenzyme; compositions thereof; process for... – Transferase other than ribonuclease
Reexamination Certificate
1994-11-18
2001-03-06
Martinell, James (Department: 1633)
Chemistry: molecular biology and microbiology
Enzyme , proenzyme; compositions thereof; process for...
Transferase other than ribonuclease
C435S091200, C536S023100
Reexamination Certificate
active
06197563
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for amplifying existing nucleic acid sequences if they are present in a test sample and detecting them if present by using a probe. More specifically, it relates to a process for producing any particular nucleic acid sequence from a given sequence of DNA or RNA in amounts which are large compared to the amount initially present so as to facilitate detection of the sequences, using a thermostable enzyme to catalyze the reaction. The DNA or RNA may be single- or double-stranded, and may be a relatively pure species or a component of a mixture of nucleic acids. The process of the invention utilizes a repetitive reaction to accomplish the amplification of the desired nucleic acid sequence.
2. Description of Related Disclosures
For diagnostic applications in particular, the target nucleic acid sequence may be only a small portion of the DNA or RNA in question, so that it may be difficult to detect its presence using nonisotopically labeled or end-labeled oligonucleotide probes. Much effort is being expended in increasing the sensitivity of the probe detection systems, but little research has been conducted on amplifying the target sequence so that it is present in quantities sufficient to be readily detectable using currently available methods.
Several methods have been described in the literature for the synthesis of nucleic acids de novo or from an existing sequence. These methods are capable of producing large amounts of a given nucleic acid of completely specified sequence.
One known method for synthesizing nucleic acids de novo involves the organic synthesis of a nucleic acid from nucleoside derivatives. This synthesis may be performed in solution or on a solid support. One type of organic synthesis is the phosphotriester method, which has been utilized to prepare gene fragments or short genes. In the phosphotriester method, oligonucleotides are prepared which can then be joined together to form longer nucleic acids. For a description of this method, see Narang, S. A., et al.,
Meth. Enzymol.,
68, 90 (1979) and U.S. Pat. No. 4,356,270. The patent describes the synthesis and cloning of the somatostatin gene.
A second type of organic synthesis is the phosphodiester method, which has been utilized to prepare a tRNA gene. See Brown, E. L., et al.,
Meth. Enzymol.,
68, 109 (1979) for a description of this method. As in the phosphotriester method, the phosphodiester method involves synthesis of oligonucleotides which are subsequently joined together to form the desired nucleic acid.
Although the above processes for de novo synthesis may be utilized to synthesize long strands of nucleic acid, they are not very practical to use for the synthesis of large amounts of a nucleic acid. Both processes are laborious and time-consuming, require expensive equipment and reagents, and have a low overall efficiency. The low overall efficiency may be caused by the inefficiencies of the synthesis of the oligonucleotides and of the joining reactions. In the synthesis of a long nucleic acid, or even in the synthesis of a large amount of a shorter nucleic acid, many oligonucleotides would need to be synthesized and many joining reactions would be required. Consequently, these methods would not be practical for synthesizing large amounts of any desired nucleic acid.
Methods also exist for producing nucleic acids in large amounts from small amounts of the initial existing nucleic acid. These methods involve the cloning of a nucleic acid in the appropriate host system, where the desired nucleic acid is inserted into an appropriate vector which is used to transform the host. When the host is cultured the vector is replicated, and hence more copies of the desired nucleic acid are produced. For a brief description of subcloning nucleic acid fragments, see Maniatis, T., et al.,
Molecular Cloning: A Laboratory Manual,
Cold Spring Harbor Laboratory, pp. 390-401 (1982). See also the techniques described in U.S. Pat. Nos. 4,416,988 and 4,403,036.
A third method for synthesizing nucleic acids, described in U.S. Pat. No. 4,293,652, is a hybrid of the above-described organic synthesis and molecular cloning methods. In this process, the appropriate number of oligonucleotides to make up the desired nucleic acid sequence is organically synthesized and inserted sequentially into a vector which is amplified by growth prior to each succeeding insertion.
The present invention bears some similarity to the molecular cloning method; however, it does not involve the propagation of any organism and thereby avoids the possible hazards or inconvenience which this entails. The present invention also does not require synthesis of nucleic acid sequences unrelated to the desired sequence, and thereby the present invention obviates the need for extensive purification of the product from a complicated biological mixture.
European Pat. Publication No. 200,362 published Dec. 10, 1986 discloses a procedure whereby existing nucleic acids may be produced in larger quantities so as to prepare other nucleic acids or to diagnose for the presence of nucleic acids. The amplification and detection process is also described by Saiki et al.,
Science,
230:1350-1354 (1985), and by Saiki et al.,
Biotechnology,
3:1008-1012 (1985). U.S. Ser. No. 899,061 filed Aug. 22, 1986, supra, now abandoned in favor of divisional application U.S. Ser. No. 07/494,174 filed Mar. 14, 1990, which issued as U.S. Pat. No. 5,038,852, discloses carrying out an amplification of nucleic acids in the presence of a thermostable enzyme in a heat-conducting block whose temperature is controlled by computer means. U.S. application Ser. No. 899,344 filed Aug. 22, 1986, supra, now abandoned in favor of continuation application U.S. Ser. No. 07/491,210, filed Mar. 9, 1990, discloses an amplification procedure followed by dot blot analysis using a heat-stable enzyme. U.S. application Ser. No. 899,241 filed Aug. 22, 1986, supra, now abandoned, discloses purification of a thermostable enzyme, preferably a polymerase from
Thermus aquaticus.
SUMMARY OF THE INVENTION
The present invention resides in a process for amplifying one or more specific nucleic acid sequences present in a nucleic acid or mixture thereof using primers and a thermostable enzyme. The extension product of one primer when hybridized to the other becomes a template for the production of the desired specific nucleic acid sequence, and vice versa, and the process is repeated as often as is necessary to produce the desired amount of the sequence. The method herein improves the specificity of the amplification reaction, resulting in a very distinct signal of amplified nucleic acid. In addition, the method herein eliminates the need for transferring reagents from one vessel to another after each amplification cycle. Such transferring is not required because the thermostable enzyme will withstand the high temperatures required to denature the nucleic acid strands and therefore does not need replacement. The temperature cycling may, in addition, be automated for further reduction in manpower and steps required to effectuate the amplification reaction.
More specifically, the present invention provides a process for amplifying at least one specific nucleic acid sequence contained in a nucleic acid or a mixture of nucleic acids, wherein if the nucleic acid is double-stranded, it consists of two separated complementary strands of equal or unequal length, which process comprises:
(a) contacting each nucleic acid strand with four different nucleoside triphosphates and one oligonucleotide primer for each different specific sequence being amplified, wherein each primer is selected to be substantially complementary to different strands of each specific sequence, such that the extension product synthesized from one primer, when it is separated from its complement, can serve as a template for synthesis of the extension product of the other primer, said contacting being at a temperature which promotes hybridization of each primer to
Erlich Henry A.
Gelfand David H.
Horn Glenn
Mullis Kary B.
Saiki Randall K.
Martinell James
Petry Douglas A.
Roche Molecular Systems Inc.
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