Coaction of DNA topoisomerase IIIalpha and a RecQ homologue during the germ-line mitosis in Caenorhabditis elegans.
BACKGROUND
Among the four RecQ homologues predicted from the Caenorhabditis elegans genomic DNA sequence, T04A11.6 is most similar to Bloom syndrome's protein in humans. To investigate a possible interaction of the protein with topoisomerase IIIalpha (TOP3alpha), as observed between TOP3 and RecQ homologues in yeast and human, the top3alpha gene expression was suppressed by RNA interference (RNAi) in the him-6(e1104) C. elegans strain which is mutated in T04A11.6 (F. Mueller & C. Wicky, personal communication).


RESULTS
Germ cells in the gonads of the progeny him-6(e1104);top3alpha(RNAi) showed severe chromosomal abnormalities and were arrested during mitosis with a subsequent failure in meiotic entry. Most of the aberrant chromosomes were stained by the TUNEL assay but not by the SYTO12 dye, suggesting extensive DNA breaks not associated with apoptosis. The phenotypes in the germ cells of him-6(e1104);top3alpha(RNAi) were also observed in the progeny produced by double RNA interference of the top3alpha and him-6 gene expression, though at a reduced level. The over-expressed TOP3alpha and Him-6 proteins showed specific physical interaction in vitro, in agreement with the genetic interaction in C. elegans.


CONCLUSIONS
In C. elegans, TOP3alpha and the RecQ homologue (T04A11.6) contribute to genome stability during germ-line mitosis, probably by acting in a complex.
Kim
You-Chan
YC
Department of Biochemistry, College of Science, Yonsei University, Seoul 120-749, Korea.
Lee
Min-Ho
MH
Ryu
Sung-Shin
SS
Kim
Ji-Hoon
JH
Koo
Hyeon-Sook
HS
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000502:physiology*; D002869:Chromosome Aberrations; D004265:DNA Helicases / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D005854:Germ Cells / Q000502:physiology; D008540:Meiosis / Q000502:physiology; D008938:Mitosis / Q000502:physiology*; D011485:Protein Binding; D012313:RNA / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D053484:RecQ Helicases
D012313:RNA; D000251:Adenosine Triphosphatases; C506725:RECQL protein, human; D004265:DNA Helicases; D053484:RecQ Helicases; D004264:DNA Topoisomerases, Type I