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Genetics of immunoglobulins: Ontogenic, biological, and clinical implications
Published in Gabriel Virella, Medical Immunology, 2019
The VDJ joining is regulated by two proteins encoded by two closely linked recombination-activating genes, RAG-1 and RAG-2, localized on the short arm of human chromosome 11. These genes have at least two unusual characteristics not shared by most eukaryotic genes: they are devoid of introns and, although adjacent in location and synergistic in function, they have no sequence homology. The latter implies that, unlike the immunoglobulin and major histocompatibility complex genes, RAG-1 and RAG-2 did not arise by gene duplication. Recent studies suggest that these genes may be evolutionarily related to transposons, genetic elements that can be transposed in the genome from one location to the other. Conserved recombination signal sequences (RSSs) serve as substrate for the enzymes coded by the RAG genes. These enzymes introduce a break between the RSS and the coding sequence. Mechanisms involved in subsequent rejoining to form a mature coding segment are not completely understood.
Mobile DNA Sequences and Their Possible Role in Evolution
Published in S. K. Dutta, DNA Systematics, 2019
Georgii P. Georgiev, Yurii V. Ilyin, Alexei P. Ryskov, Tatiana I. Gerasimova
The nucleotide sequence of simple FB elements shows that they do not encode proteins. Thus, they do not produce a machinery for transposition and should be considered as passive transposons. The presence of inverted repeats at their ends suggests the involvement of an excision-insertion transposition mechanism using “transposase(s)”. Indeed, it was found that in P-M dysgenesis the transposition of FB-elements, possibly induced by the P-factor product, was strikingly increased.95
The Concept of Health
Published in Dien Ho, A Philosopher Goes to the Doctor, 2019
The fact that transposons make up the bulk of our DNA and have been embedded in us for eons make them no longer temporary residents but a part of our genome. They are like obnoxious manipulative family members whom we can’t get rid of. When philosophers speak of the evolutionary purpose of a subsystem or a genotype in our genome, they must include these transposons. Although some of them provide benefits to the host (or more accurately, the parts of our genome that have phenotypical expressions), many of them are either benign or nasty. Their evolutionary purposes do not coincide with ours, let alone our health. The complexity of our genes, filled with fossil genes left over from our ancestors and transposons of all stripes, means that the idea of there being clear and unified evolutionary purposes is unsustainable. It is like looking at Grand Central Station and asking about the destination where everyone wishes to go. Worse still, some of the travelers might work against you to ensure that they get to their destinations at your expense. From this chaotic jumble we emerge, and it is important to remember that not everything in our body put there by natural selection has our best interests in mind.
Effects of the COVID-19 pandemic: new approaches for accelerated delivery of gene to first-in-human CMC data for recombinant proteins
Published in mAbs, 2023
Hervé Broly, Jonathan Souquet, Alain Beck
The engineered Tc1/mariner transposons named Sleeping Beauty and Frog Prince, the insect-derived natural element Piggy-Bac and the Leap-In Transposase use transposon-based vectors and a cognate transposase enzyme.70–72 Transposition stably inserts multiple independent copies of structurally intact transposons. The Leap-In Transposase system associates CHO-GSKO host cells and transposition, thus leading to more homogeneous stable pools with high gene copy number, higher productivity, and better comparability between pools and clones. Especially, the multiplicity of the insertion sites de-risks the use of cell pools instead of a clonal cell line for producing material for toxicological studies because of higher reliability of expression stability, productivity, and product quality profile.73
Porphyromonas gingivalis and its CRISPR-Cas system
Published in Journal of Oral Microbiology, 2019
Transposase is an enzyme that binds to the two ends of a transposon and bring them together to form a loop. It then catalyzes movement of the transposon to another part of the genome by a cut and paste mechanism or replicative transposition. In the study by Chen et al. [23] who did comparative genomics of 19 P. gingivalis strains, a high prevalence of transposase proteins was found encoded in P. gingivalis (Table 2); actually as much as 149 copies in strain A7436. In another study transposases were found in all of the 35 genomes of P. gingivalis examined, varying in number from 8 (strains Ando, F0185, SDJ5) to 103 (A7436) [28]. The lower number of transposases detected in the original genomes that were not completely sequenced in this study was most likely due to the in-between-contig sequence gaps that may contain highly repeated sequences such as transposases and IS elements. The completed genome with the lowest number of mobility-related genes was that of strain A7A1-28, where 68 transposases were detected.
Transposon mutagenesis in oral streptococcus
Published in Journal of Oral Microbiology, 2022
Yixin Zhang, Zhengyi Li, Xin Xu, Xian Peng
Transposons are mobile genetic factors that can move within genomes through ‘cut and paste’ or copy mechanisms. A transposase encoded by a transposon can recognise specific inverted repeat sequences at both ends of the transposon, separate the transposon from adjacent sequences, and insert it into a DNA target site [31]. The most common application of transposons is insertional mutagenesis, which can be used to create libraries of mutant strains. The success of transposon mutant library screening depends on the number of mutants screened and diversity of the library.