Note for: Homologous DNA recombination in vertebrate cells

Note for: Homologous DNA recombination in vertebrate cells

(doi: 10.1073/pnas.111006398)

Rad52 =RAD50, RAD51, RAD52, RAD54, RDH54/TID1, RAD55, RAD57, RAD59, MRE11, and XRS2.

Primary structure is this group of protein is very conserved from yeast to human.

This paper mentioned that though the gene structure is very conserved across the kingdoms but the phenotype regarding what has been observed in yeast cannot be implied in vertebrate.

This review paper wants to point out the difference.

even though, the DT40 cell is transformed by leukosis their property on gene conversion still remains.

Not only DT40, other avian leukosis virus cell line-RP9 and v-rel-transformed cell lines-->high targeted as well.

molecular mechanism for high targeting efficiencies are not clear.

Observation;

Gene that relates to gene conversion in Ig gene conversion might also promote the gene targeting efficiencies since these two processes use HR.

Advantage of DT40;

1. invariant character of DT40 cells after repetitively subculture

2. be able to do gene targeting with 7 different selectable markers.

3. contain complementary DNA repair--easy to study DNA repair once either has defected.

4. growth rate is fast, 8-10 hrs, easy to observe the phenotype.

5. bc of the lack of p53, allow us to study the mutant that caused genome instability.

 

In vertebrate;

Rad51 and Rad54 are not expressed at G0 even after genotoxic treatment, contradictorily, in yeast - those can be induced by genotoxic treatment.

Conditional KO- Temperature sensitive

Rad52 in vertebrate plays less important role than Rad51, which is contradicting to yeast Rad52 is more important.

They mentioned the same homolog was not necessary to perform the same function in different species. In this case, the authors mentioned the differences between S. cerevisiae and S. pombe (Rad32 is homologous to Mre11 in S. cerevisiae).

No BRCA2 homologs in yeast. More numbers of Rad51 paralogs in vertebrate rather than in yeast. The complexity might relate to genome size which required more time to check/repair the damage - besides including the cell cycle control.

DT40 is a good model for studying DNA recombination.