TY - JOUR

T1 - F9 embryonal carcinoma cells fail to stop at G1/S boundary of the cell cycle after gamma-irradiation due to p21(WAF1/CIP1) degradation

AU - Malashicheva, AB

AU - Kislyakova, TV

AU - Aksenov, ND

AU - Osipov, KA

AU - Pospelov, VA

PY - 2000/8/10

Y1 - 2000/8/10

N2 - We studied the ability of F9 teratocarcinoma cells to arrest in G1/S and G2/M checkpoints after gamma-irradiation, Wild-type p53 protein was rapidly accumulated in F9 cells after gamma-irradiation, however, this was followed not by a G1/S arrest but by a short and reversible delay of the cell cycle in G2/M. In order to elucidate the reasons of the lack of G1/S arrest in F9 cells, we investigated the expression of p53 downstream target Cdk inhibitor p21(WAF1/CIP1). In spite of p53-dependent activation of p21(WAF1/CIP1) gene promoter and p21(WAF1/CIP1) mRNA accumulation upon irradiation, the p21(WAF1/CIP1) protein was not detected by either immunoblot or immunofluorescence techniques. However, the cells treated with a specific proteasome inhibitor lactacystin revealed the p21(WAF1/CIP1) protein both in non-irradiated and irradiated cells. Therefore we suggest that p21(WAF1/CIP1) protein is degraded by a proteasome-dependent mechanism in F9 cells and the lack of G1/S arrest after gamma-irradiation is due to this degradation. We also examined the expression and activity of cell cycle regulatory proteins: G1- and G2-cyclins and cyclin-dependent kinases, In the absence of functional p21(WAF1/CIP1) inhibitor, the activity of G1 cyclin/Cdk complexes was insufficiently inhibited to cause a G1 arrest, whereas a decrease of cdc2 and cyclin B1-associated kinase activities was enough to contribute to a reversible G2 arrest following gamma-irradiation. After gamma-irradiation, the majority of F9 cells undergo apoptosis implying that wt-p53 likely triggers pro-apoptotic gene expression in DNA damaged cells. Elimination of defected cells might ensure maintenance of genome integrity in the remaining cell population.

AB - We studied the ability of F9 teratocarcinoma cells to arrest in G1/S and G2/M checkpoints after gamma-irradiation, Wild-type p53 protein was rapidly accumulated in F9 cells after gamma-irradiation, however, this was followed not by a G1/S arrest but by a short and reversible delay of the cell cycle in G2/M. In order to elucidate the reasons of the lack of G1/S arrest in F9 cells, we investigated the expression of p53 downstream target Cdk inhibitor p21(WAF1/CIP1). In spite of p53-dependent activation of p21(WAF1/CIP1) gene promoter and p21(WAF1/CIP1) mRNA accumulation upon irradiation, the p21(WAF1/CIP1) protein was not detected by either immunoblot or immunofluorescence techniques. However, the cells treated with a specific proteasome inhibitor lactacystin revealed the p21(WAF1/CIP1) protein both in non-irradiated and irradiated cells. Therefore we suggest that p21(WAF1/CIP1) protein is degraded by a proteasome-dependent mechanism in F9 cells and the lack of G1/S arrest after gamma-irradiation is due to this degradation. We also examined the expression and activity of cell cycle regulatory proteins: G1- and G2-cyclins and cyclin-dependent kinases, In the absence of functional p21(WAF1/CIP1) inhibitor, the activity of G1 cyclin/Cdk complexes was insufficiently inhibited to cause a G1 arrest, whereas a decrease of cdc2 and cyclin B1-associated kinase activities was enough to contribute to a reversible G2 arrest following gamma-irradiation. After gamma-irradiation, the majority of F9 cells undergo apoptosis implying that wt-p53 likely triggers pro-apoptotic gene expression in DNA damaged cells. Elimination of defected cells might ensure maintenance of genome integrity in the remaining cell population.

KW - p21(WAF1/CIP1)

KW - p53

KW - G1 and G2 arrests

KW - teratocarcinoma F9

KW - gamma-irradiation

KW - RADIATION-INDUCED APOPTOSIS

KW - WILD-TYPE P53

KW - DNA-DAMAGE

KW - TERATOCARCINOMA CELLS

KW - SPINDLE DISRUPTION

KW - TRANSFORMED-CELLS

KW - RETINOIC ACID

KW - STEM-CELLS

KW - DIFFERENTIATION

KW - CHECKPOINT

U2 - 10.1038/sj.onc.1203736

DO - 10.1038/sj.onc.1203736

M3 - статья

VL - 19

SP - 3858

EP - 3865

JO - Oncogene

JF - Oncogene

SN - 0950-9232

IS - 34

ER -