Difference between revisions of "General Information/ IS derivatives of Tn3 family transposons"
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− | |[[Image:1.15.1.png|thumb|center|510x510px|'''Fig. 1.15.1.''' Tn''3'' family characteristics.<br /> | + | |[[Image:1.15.1.png|thumb|center|510x510px|'''Fig. 1.15.1.''' Tn''3'' family characteristics.<br />Transposons are shown as yellow boxes with their names on the left and their lengths on the right. Terminal inverted repeats are shown as black arrowheads within the box. Transposition-related genes (transposases and resolvase recombinases are shown as purple arrows), passenger genes as red arrows, for antibiotic resistance orange/yellow arrows for heavy metal resistance, bright yellow for plant pathenogenicity genes orange for toxin/antitoxin genes and blue for integron integrase genes. Resolution sites are shown in green. |
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+ | Note that Tn''1071'' carries only a transposase gene and therefore could be considered an Insertion sequence.|alt=|border]] | ||
|[[Image:1.15.2.png|thumb|center|510x510px|'''Fig. 1.15.2.''' Tn''3'' family resolvase configuration. | |[[Image:1.15.2.png|thumb|center|510x510px|'''Fig. 1.15.2.''' Tn''3'' family resolvase configuration. | ||
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+ | A) Tn''3'' has divergent transposase and resolvase (serine recombinase) genes with a res (resoluion, recombination site between the divergent genes. It includes 3 sites at which resolvase binds (I, II and III). | ||
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+ | B) Tn''501'' carries co-linear transposase and resolvase genes with the res site upstream of the resolvase. | ||
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+ | C) Tn''4430'' has a similar configuration as Tn501but its resolvase is a tyrocine recombinase and its res site, upstream of the resolvase has a more complex structure | ||
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+ | D) TnXax1 carries two divergent genes, tnpS (a serine recombinase) and tnpT (a helper gene). The resolution site lies between the two genes and has a complex structure. |alt=]] | ||
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==Bibliography== | ==Bibliography== | ||
<references /> | <references /> |
Revision as of 13:24, 7 May 2020
Another source of ambiguity for classification purposes occurs in the Tn3 family (see section “Tn families”) (Fig.1.15.1 and 1.15.2). Tn3 family members are quite variable. They include a number of diverse passenger genes that can represent entire operons, notably mercury resistance, or individual genes involved in antibiotic resistance, breakdown of halogenated aromatics, or virulence [e.g. [1]]]. They often carry integron recombination platforms enabling them to incorporate additional resistance genes by recruiting integron cassettes[2]. Members are quite characteristic: they have long relatively well conserved IR and a particularly long Tpase (950 to 1025 aa). They also encode a site-specific recombination (“resolution”) system necessary for completion of their transposition[3]. There are a number of different resolution systems associated with different members of this family (Fig.1.15.2) IS1071, (Fig.1.15.1) composed of Tn3-like IR and Tpase gene but lacking both the site-specific recombination system and passenger genes was identified many years ago[4][5]. This clearly accords with the definition of an IS. Several other examples have now been identified (e.g. ISVsa19, ISShfr9, ISBusp1).