China
Africa
Explore chapters and articles related to this topic
Advances in Genome Editing
Published in Yashwant Pathak, Gene Delivery, 2022
CRISPR–Cas is a bacterial adaptive immune system that cleaves invading nucleic acids. CRISPRs were first discovered in E. coli in 1987 during an examination of genes involved in phosphate metabolism, and later in a variety of other bacterium species (Ishino et al., 2018). CRISPR-Cas systems are classified into two groups (class I and II), based on the structural variation of the Cas genes and the way they are organized. The classes are further subdivided into six types (type I–VI). Class I includes type I, III, and IV, and class II includes type II, V, and VI (Makarova and Koonin, 2015). Class 1 CRISPR–Cas systems have multiprotein effector complexes, whereas class II systems only have a single effector protein. Presently, six subtypes of the Type I system (Type I-A through Type I-F) have been found, each with a different number of Cas genes. All Type I systems, with the exception of cas1, cas2, and cas3, encode a Cascade-like complex. Cascade is the name given to the effector complex of type I systems (CRISPR-associated complex for antiviral defense) (Brouns et al., 2008). Cascade engages crRNA and locates the target, and the majority of variations are also in charge of crRNA processing. In rare circumstances, cascade can also help with spacer acquisition. Cas3 is a component of the Cascade complex in the Type I-A system, a protein with both helicase and DNase domains responsible for degrading the target (Huo et al., 2014; Gong et al., 2014). Cas1 and Cas2, the Cas9 hallmark protein, and occasionally a fourth protein are encoded by Type II CRISPR-Cas systems (Csn2 or Cas4) (Chylinski et al., 2014). Cas9 helps with adaptation, engages in crRNA processing, and cleaves the target DNA with the help of crRNA and tracrRNA (Karvelis et al., 2013). Type II systems are split into subtypes II-A, II-B, and II-C. In Type II-A and Type II-B, respectively, the csn2 and cas4 genes encoding adaptation proteins are present, whereas Type II-C lacks a fourth gene (Rath et al., 2015). The Type III CRISPR-Cas systems contain the hallmark protein Cas10 with unclear function (Dorsey et al., 2019).
Induction of caspase-2 gene expression in carboxyl-functionalized carbon nanotube-treated human T-cell leukemia (Jurkat) cell line
Published in Drug and Chemical Toxicology, 2021
Shirin Lotfipanah, Majid Zeinali, Parichehreh Yaghmaei
Jurkat cells were exposed to either carboxylated SWCNT or carboxylated MWCNT at a fixed concentration of 100 µg ml−1 for 72 h and then the expression levels of some caspase genes (Cas2, Cas4, Cas6, Cas8, and Cas10) were measured using qRT-PCR technique for investigating CNT-induced apoptosis. Some differences in the expression levels of caspase genes were seen in the CNT-treated Jurkat cells compared to the untreated control groups (Table 2). Expression level of Cas2 gene was increased significantly in the Jurkat cells treated with either carboxylated MWCNT (6.08-fold), or carboxylated SWCNT (1.2-fold) in comparison to the untreated control group. A mild but not significant increase in the expression levels of Cas4, Cas8, and Cas10 genes were also observed in the Jurkat cells treated with carboxylated SWCNT. In the Jurkat cells treated with carboxylated MWCNT, a mild but not significant increase in the expression levels of Cas6 and Cas10 genes were also seen (Table 2).
CRISPR/Cas: from adaptive immune system in prokaryotes to therapeutic weapon against immune-related diseases
Published in International Reviews of Immunology, 2020
Juan Esteban Garcia-Robledo, María Claudia Barrera, Gabriel J. Tobón
In the last two decades, the genomic revolution has allowed a more in-depth study of gene sequences, including CRISPR repetitions [27]. The accumulation of gene sequences in genomic libraries from many species has allowed for genomic comparison of CRISPR loci among prokaryotic organisms. Early comparative analyses revealed four highly conserved genes adjacent to these repeated palindromic CRISPR regions encoding the Cas proteins Cas1 − 4. In the intervening years, many additional Cas proteins have been described and categorized into different subtypes. Cas9 is a nuclease used by Type II CRISPR systems for genetic silencing [30, 36, 37]. Comparative genomics studies have also demonstrated that Cas3 and Cas4 are present mainly in bacteria and thermophilic archaea [27, 30, 38] and contain motifs characteristic of superfamily 2 helicases and RecB exonucleases, respectively. These findings further implicated CRISPR/Cas systems in DNA repair and recombination.