Integron

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Integrons are genetic units characterized by their ability to capture and incorporate gene cassettes by site-specific recombination.

Discovery[edit]

They were initially discovered in relation to antibiotic resistance.[1]

Structure[edit]

An integron is minimally composed of:[2][3]

  • a gene encoding for a site-specific recombinase: intI, belonging to the integrase family
  • a proximal recombination site: attI, which is recognized by the integrase[4] and at which gene cassettes may be inserted
  • a promoter: Pc, which directs transcription of cassette-encoded genes

Gene Cassettes[edit]

Main article: Gene cassettes

Additionally, an integron will usually contain one or more gene cassettes that have been incorporated into it. The gene cassettes may encode genes for antibiotic resistance, although most genes in integrons are uncharacterized. An attC sequence (also called 59-be) is a repeat that flanks cassettes and enables cassettes to be integrated at the attI site, excised and undergo horizontal gene transfer.

Occurrence[edit]

Integrons may be found as part of mobile genetic elements such as plasmids and transposons. Integrons can also be found in chromosomes.

Terminology[edit]

The term super-integron was first applied in 1998 (but without definition) to the integron with a long cassette array on the small chromosome of Vibrio cholerae.[5][6] The term has since been used for integrons of various cassette array lengths or for integrons on bacterial chromosomes (versus, for example, plasmids). Use of "super-integron" is now discouraged since its meaning is unclear.[5]

References[edit]

  1. ^ Integrons: agents of bacterial evolution (Mazel 2006), Nature Reviews Microbiology 4, 608-620 | doi:10.1038/nrmicro1462
  2. ^ Kovalevskaya, N. P. (2002). Molecular Biology 36 (2): 196. doi:10.1023/A:1015361704475. 
  3. ^ Hall R, Collis C, Kim M, Partridge S, Recchia G, Stokes H (1999) Mobile gene cassettes and integrons in evolution. Ann. New York Acad. Sci. 870:68–80.
  4. ^ Hall, RM; Collis, CM (1995). "Mobile gene cassettes and integrons: Capture and spread of genes by site-specific recombination". Molecular microbiology 15 (4): 593–600. PMID 7783631. 
  5. ^ a b Hall, R. M.; Stokes, HW (2004). "Integrons or super integrons?". Microbiology 150 (Pt 1): 3–4. doi:10.1099/mic.0.26854-0. PMID 14702391. 
  6. ^ Mazel, D.; Dychinco, B; Webb, VA; Davies, J (1998). "A Distinctive Class of Integron in the Vibrio cholerae Genome". Science 280 (5363): 605–8. doi:10.1126/science.280.5363.605. PMID 9554855. 

Further reading[edit]

External links[edit]