Difference between revisions of "General Information/Influence of transposition mechanisms on genome impact"
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|[[Image:1.23.2.png|thumb|center|500x500px|'''Fig 1.23.2.''' Inter- and Intra-molecular replicative transposition.'''Top'''. Inter-molecular transposition. Cleavage at both TIRs of the IS results in nicks on both | |[[Image:1.23.2.png|thumb|center|500x500px|'''Fig 1.23.2.''' Inter- and Intra-molecular replicative transposition.'''Top'''. Inter-molecular transposition. Cleavage at both TIRs of the IS results in nicks on both | ||
− | strands, generating 3=-OH groups | + | strands, generating 3=-OH groups that attack the target site, leading to the formation of a Shapiro intermediate. DNA replication generates the cointegrate containing a duplication of the IS and the target site. The cointegrate can be subsequently resolved into a plasmid identical to the original donor plasmid and a modified target plasmid carrying a copy of the IS flanked by TSDs arranged as direct repeats. |
− | '''Bottom'''. Intra-molecular transposition. When an IS targets a target site in the same replicon, cleavages at both TIRs generate 3=-OH groups that can either attack the target site on the same strand (cis) or the opposite strand (trans). In the cis pathway, DNA between the IS and target site (dashed lines) becomes circularized and contains one IS copy and target site. In the trans pathway, DNA between IS and target site is instead inverted (“a b” becomes “b a”), bracketed by the original IS and a new copy in an inverted orientation. The target site is also duplicated but in inverted orientation, and each TSD is associated with one IS copy.|alt=]]<br /> | + | '''Bottom'''. Intra-molecular transposition. When an IS targets a target site in the same replicon, cleavages at both TIRs generate 3=-OH groups that can either attack the target site on the same strand (cis) or the opposite strand (trans). In the cis pathway, DNA between the IS and target site (dashed lines) becomes circularized and contains one IS copy and target site. In the trans pathway, DNA between IS and the target site is instead inverted (“a b” becomes “b a”), bracketed by the original IS, and a new copy in an inverted orientation. The target site is also duplicated but in an inverted orientation, and each TSD is associated with one IS copy.|alt=]]<br /> |
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==Bibliography== | ==Bibliography== | ||
<references /> | <references /> |
Revision as of 21:08, 22 May 2020
The way in which strand cleavages and transfers occur during transposition also affects the outcome of the transposition events and therefore impinges on genome structure. For IS with DDE Tpases, Tn3 and IS6 family members generate fusions or cointegrates between the donor and target replicons by a process of replicative transposition, presumably by Target Primed Replicative Transposition (TPRT)[1][2][3] (Fig.1.23.1 and Fig.1.23.2 top). However, in the event of intramolecular transposition, this type of mechanism is expected to give rise to inversions with a copy of the IS at each junction or inversions with a single IS copy remaining and a second copy segregating with a circularized deletion[4] (Fig.1.23.2 botton; see [5]). Note that similar effects are also known to occur by homologous recombination between two inverted or directly repeated IS copies in a replicon. Other known mechanisms such as cut-and-paste, or copy-and-paste (Donor Primed Replicatice Transposition; DPRT)[6] would not generate this type of genomic rearrangement but could contribute to genomic modifications in other ways such as “nearly precise excision”[7] or by using alternative sequences which resemble their IR[8][9].
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