homologous recombination: why not?
lichten%bchem.dnet at DXI.NIH.GOV
Thu Sep 30 17:08:33 EST 1993
Dave Rose writes:
>Does anyone know why it is exactly that yeast has homologous
>recombination while most other systems don't (at least not very
No. Not exactly. But the real question is why yeast doesn't repair
nonhomologously (see below).
>i.e. is there some selective advantage to being able to do
>this or is it a biproduct of a repair pathway that doesn't exist in most
Don't assume that most organisms don't do homologous recombination
--they do. It's just that in most cases, a nonhomologous system prevails
with exogenously added DNA. There are exceptions--for example, avian pre-B
cells, which target exogenous DNA with relatively high fidelity (Jean-Marie
Buerstedde and coworkers). And it isn't that clear to me that "other
systems" don't do most of their repair of breaks on chromosomal DNA
homologously. Anyone out there know of any data?
Also note that, absent homology, yeast will integrate nonhomologously (Bob
Scheistl and Tom Petes).
Finally, it should be pointed out that, although S. cerevisiae repairs
double-strand breaks on its _chromosomes_ very efficiently by homologous
recombination, it is not at all clear what the efficiency of homologous
repair of exogenously added DNA is. It may very well be that other systems
are just as "efficient" at homologous integration of exogenously added, non
-chromosomal DNA as is yeast, but that yeast is defficient in or turned way
down for nonhomologous integration.
This doesn't answer your question, but maybe will help you reconsider it.
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