Naslov
Virtues and vices of exogenous DNA integration

Autori
Gjuračić, Krešimir

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, neobjavljeni rad, znanstveni

Izvornik
ICGEB Course: Genome Dynamics and Evolution 2004 / - Trst, 2004

Skup
ICGEB Course: "Genome Dynamics and Evolution"

Mjesto i datum
Trst, Italija, 22.03.2004. - 25.03.2004

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
yeast; homologous recombination; illegitimate recombination; gene transfer

Sažetak
Exchange of genetic material between different species, also called horizontal or lateral gene transfer, is considered as a major force in unicellular organism evolution. In natural habitats huge variety of unicellular organisms live together, frequently using each other as food and consequently are constantly exposed to exogenous DNA. One of the horizontal gene transfer mechanisms is the integration of exogenous DNA into host genome. Although this event can produce an evolutionary benefit for the host cell, it can also seriously compromise the genome integrity and subsequently cell survival. Therefore, unicellular organisms have developed numerous defence strategies against invading exogenous DNA. One of the well known strategies is the restriction-modification (R-M) system, based on discrimination between exo- and endogenous DNA by specific identification mark i.e. methylation of specific nucleotide sequence, and subsequent degradation of recognized invading DNA. The R-M system is specific for bacteria with no equivalent in eukaryotic organisms. Horizontal gene transfer by means of transformation commonly occur in contemporary molecular biology laboratories. The yeast Saccharomyces cerevisiae is one of the most studied unicellular eukaryotes mainly due to relatively high efficiency of targeted genetic modifications that could be done in this organism. However, efficient yeast transformation was possible after development of complex protocols which avoid inherent yeast defence mechanisms against invading exogenous DNA. On the basis of various transformation experiments of yeast and other unicellular eukaryotes, here are proposed some initial ideas about different levels of this defence mechanisms: DNase activity associated with cell wall/periplasm compartment, ligation of incoming linear DNA with mitochondrial fragments and formation of mitoticaly unstable genetic elements, preferential DNA integration into repetitive genomic regions and subsequent "genome cleaning" by recombination between directed repeats, and "homology search" as probably the major barrier for exogenous DNA integration. Even in the case of yeast transformation with homologous DNA, its integration happens preferentially within noncoding DNA sequences, as another protection of genetic information encoded by ORF sequences. Taken together described phenomena strongly suggest that also unicellular eukaryotes have various strategies for genome integrity protection from exogenous DNA integration.

Izvorni jezik
Engleski

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