“CRISPR-Cas systems” in bacteria and viruses identify and destroy invading viral sequences. It is bacterial and archaeal immune system for protection against viral infections. In 2012, CRISPR-Cas system was recognised as a जीनोम editing tool. Since then, wide range of CRISPR-Cas systems have been developed and have found applications in areas such as in gene therapy, diagnostics, research and crop improvement. However, currently available CRISPR-Cas systems have limited clinical use due to frequent occurrences of off-target editing, unexpected DNA mutations and inheritable problems. Researchers have recently reported a novel CRISPR-Cas system that can target and destroy mRNA and प्रोटीन associated with different genetic diseases more accurately without off-target impact and inheritable problems. Named Craspase, it is the first CRISPR-Cas system that shows प्रोटिन editing function. It is also the first system that can edit both RNA and प्रोटिन. Because Craspase overcomes many limitations of existing CRISPR-Cas systems, it has potential to revolutionise gene therapy, diagnostics and monitoring, biomedical research, and crop improvement.
“CRISPR-Cas system” is natural immune system of bacteria and archaea against viral infections that identifies, binds and degrades the sequences in the viral gene to protect. It consists of two parts – bacterial RNA transcribed from the viral gene incorporated in the bacterial genome after first infection (called CRISPR, this identifies the target sequences of the invading viral genes) and an associated destroyer प्रोटिन called “CRISPR associated प्रोटिन (Cas)” which binds and degrades the identified sequences in the viral gene to protect the bacteria against viruses.
क्रिसपर stands for “clustered regularly interspaced short palindromic repeats”. It is transcribed bacterial RNA characterised by palindromic repeats.
Palindromic दोहोरिने (CRISPRs) को अनुक्रम मा पहिलो पटक पत्ता लगाइयो ई कोलाई in 1987. In 1995, Francisco Mojica observed similar structures in archaea, and it was he who first thought of these as a part of the immune system of bacteria and archaea. In 2008, it was experimentally demonstrated for the first time that the target of the immune system of bacteria and archaea was foreign DNA and not mRNA. The mechanism of identification and degradation viral sequences suggested that such systems could be used as a tool for जीनोम सम्पादन. Since its recognition as a genome editing tool in 2012, CRISPR–Cas system has come a very long way as a firmly established standard जीन सम्पादन system and has found a wide range of applications in biomedicine, agriculture, pharmaceutical industries including in clinical gene therapy1,2.
एक विस्तृत दायरा CRISPR-Cas systems are already identified and currently available for monitoring and editing DNA/RNA sequences for research, drug screening, diagnostics and treatments. The current CRISPR/Cas systems are divided into 2 classes (Class 1 and 2) and six types (Type I to XI). Class 1 systems have multiple Cas प्रोटीन which need to form a functional complex to bind and act on their targets. On the other hand, Class 2 systems have only one large Cas प्रोटिन for binding and degrading target sequences which makes Class 2 systems easier to use. Commonly used Class 2 systems are Cas 9 Type II, Cas13 Type VI, and Cas12 Type V. These systems may have undesired collateral effects I.e., off-target impact and cytotoxicity3,5.
जीन थेरापीहरू based on current CRISPR- Cas systems have limited clinical use because of frequent occurrences of off-target editing, unexpected DNA mutations, including big DNA fragment deletions and large DNA structural variants at both on-target and off-target sites that leads to cell deaths and other inheritable problems.
क्र्यास्पेस (वा CRISPR-निर्देशित क्यास्पेस)
Researchers have recently reported a novel CRISPER-Cas system which is a Class 2 Type III-E Cas7-11 system associated with a caspase-like प्रोटिन hence named क्र्यास्पेस वा CRISPR-निर्देशित क्यास्पेस 5 (Caspases are cysteine proteases that play key role in apoptosis in breaking down cellular structures). It has potential applications in areas like gene therapy and diagnostics. Craspase is RNA-guided and RNA-targeted and do not get involved with the DNA sequences. It can target and destroy mRNA and प्रोटीन associated with different genetic diseases more accurately without off-target impact. Thus, elimination of genes associated with diseases is possible by cleavage at mRNA or protein level. Also, when linked with specific enzyme, Craspase can also be used to modify functions of proteins. When its RNase and protease functions are removed, Craspase becomes deactivated (dCraspase). It has no cutting function but binds with RNA and protein sequences. Therefore, dCraspase can be used in diagnostics and imaging to monitor and diagnose diseases or viruses.
Craspase is the first CRISPR-Cas system that shows protein editing function. It is also the first system that can edit both RNA and protein. Its जीन सम्पादन function comes at minimal off-target effects and no inheritable problems. Hence, Craspase is likely to be safer in clinical use and therapeutics than other currently available CRISPR- Cas systems 4,5.
किनभने क्र्यास्पेसले अवस्थित CRISPR-Cas प्रणालीहरूको धेरै सीमितताहरू पार गर्दछ, यसले जीन थेरापी, निदान र अनुगमन, बायोमेडिकल अनुसन्धान, र बाली सुधारमा क्रान्तिकारी परिवर्तन गर्ने सम्भावना छ। क्लिनिकल परीक्षणहरूमा सुरक्षा र प्रभावकारिता प्रमाणित गर्नु अघि कोशिकाहरूमा रोग निम्त्याउने जीनहरूलाई सटीक रूपमा लक्षित गर्न भरपर्दो वितरण प्रणाली विकास गर्न थप अनुसन्धान आवश्यक छ।
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सन्दर्भ:
- Gostimskaya, I. CRISPR-Cas9: A History of Its Discovery and Ethical Considerations of Its Use in Genome Editing। बायोकेमिस्ट्री मस्को ८७, ७७७–७८८ (२०२२)। https://doi.org/10.1134/S0006297922080090
- चाओ ली एट अल 2022. CRISPR/Cas Genome सम्पादनका लागि कम्प्युटेशनल उपकरण र स्रोतहरू। जीनोमिक्स, प्रोटियोमिक्स र बायोइन्फर्मेटिक्स। २४ मार्च २०२२ मा अनलाइन उपलब्ध। DOI: https://doi.org/10.1016/j.gpb.2022.02.006
- भ्यान बेलजोउ, SPB, Sanders, J., Rodríguez-Molina, A. et al. RNA-लक्ष्यीकरण CRISPR-Cas प्रणालीहरू। Nat Rev Microbiol 21, 21-34 (2023)। https://doi.org/10.1038/s41579-022-00793-y
- चुनी हु एट अल 2022. क्र्यास्पेस एक CRISPR RNA-निर्देशित, RNA-सक्रिय प्रोटीज हो। विज्ञान। २५ अगस्ट २०२२। भोल्युम ३७७, अंक ६६१२। पृष्ठ १२७८-१२८५। DOI: https://doi.org/10.1126/science.add5064
- Huo, G., Shepherd, J. & Pan, X. Craspase: A उपन्यास CRISPR/Cas डुअल जीन सम्पादक। कार्यात्मक र एकीकृत जीनोमिक्स 23, 98 (2023)। प्रकाशित: 23 मार्च 2023। DOI: https://doi.org/10.1007/s10142-023-01024-0
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