TY - JOUR
T1 - Recombinational repair is essential for the maintenance of chromosomal integrity in cycling vertebrate cells
AU - Takeda, S.
AU - Sonoda, E.
AU - Takata, M.
AU - Morrison, C.
AU - Tachiiri, S.
AU - Yamaguchi-Iwai, Y.
PY - 1998
Y1 - 1998
N2 - A single unrepaired double-strand break (DSB) in chromosomal DNA is enough to kill a cell. Accordingly, cells have developed several means to repair such lesions: Homologous recombinational (HR) repair and nonhomologous end joining (NHEJ) are two major cellular repair pathways for DSBs. Both pathways are conserved from yeast to mammals. Rad51 as well as Rad54 is involved in HR and expressed in cycling but not in resting cells, while Ku is involved in the NHEJ pathway, which is constitutively active. Rad51 is a homologue of the E. coli RecA protein and a key component of HR. While yeast can proliferate without RadSl, its deficiency is lethal in murine ES cells, indicating that RadSl is essential for higher,eukaryotes. To define the role of Rad51 in higher eukaryotes, we generated conditionally Rad51-deficient cells from the chicken cell line DT40, where targeted integration occurs as frequently as random integration. After Rad51 depletion, most cells accumulated in G2 with some cells undergoing mitosis before cell death. Chromosomal analysis revealed that they had chromosome-type breaks ( 1.5/cell), which were randomly distributed. This observation indicates that a small number of random DSBs occurred spontaneously during the cell cycle of higher eukaryotes. This illuminates the importance of the DSB repair system for the maintenance of genetic integrity during proliferation. Since higher eukaryotic cells carry a much larger genome than yeast cells, HR plays a more important role in the maintenance of chromosome integrity in higher eukaryotic cells than in yeast. To define the roles of the two pathways, we generated DT40 cells defective in both pathways. Spontaneous chromosomal aberrations and apoptosis were observed in both aRad54 and 4Rad54/4Ku cells, with 4Rad54/4Ku cells exhibiting significantly higher levels of chromosomal aberrations than 4Rad54 cells. These observations provide the first genetic evidence that both repair pathways play a role in maintaining chromosomal DNA. This in turn suggests that DSB repair defects might underlie chromosome instability associated with tumorigenesis.
AB - A single unrepaired double-strand break (DSB) in chromosomal DNA is enough to kill a cell. Accordingly, cells have developed several means to repair such lesions: Homologous recombinational (HR) repair and nonhomologous end joining (NHEJ) are two major cellular repair pathways for DSBs. Both pathways are conserved from yeast to mammals. Rad51 as well as Rad54 is involved in HR and expressed in cycling but not in resting cells, while Ku is involved in the NHEJ pathway, which is constitutively active. Rad51 is a homologue of the E. coli RecA protein and a key component of HR. While yeast can proliferate without RadSl, its deficiency is lethal in murine ES cells, indicating that RadSl is essential for higher,eukaryotes. To define the role of Rad51 in higher eukaryotes, we generated conditionally Rad51-deficient cells from the chicken cell line DT40, where targeted integration occurs as frequently as random integration. After Rad51 depletion, most cells accumulated in G2 with some cells undergoing mitosis before cell death. Chromosomal analysis revealed that they had chromosome-type breaks ( 1.5/cell), which were randomly distributed. This observation indicates that a small number of random DSBs occurred spontaneously during the cell cycle of higher eukaryotes. This illuminates the importance of the DSB repair system for the maintenance of genetic integrity during proliferation. Since higher eukaryotic cells carry a much larger genome than yeast cells, HR plays a more important role in the maintenance of chromosome integrity in higher eukaryotic cells than in yeast. To define the roles of the two pathways, we generated DT40 cells defective in both pathways. Spontaneous chromosomal aberrations and apoptosis were observed in both aRad54 and 4Rad54/4Ku cells, with 4Rad54/4Ku cells exhibiting significantly higher levels of chromosomal aberrations than 4Rad54 cells. These observations provide the first genetic evidence that both repair pathways play a role in maintaining chromosomal DNA. This in turn suggests that DSB repair defects might underlie chromosome instability associated with tumorigenesis.
UR - https://www.scopus.com/pages/publications/33748596862
M3 - Article
AN - SCOPUS:33748596862
SN - 0301-472X
VL - 26
SP - 738
JO - Experimental Hematology
JF - Experimental Hematology
IS - 8
ER -