Overexpression of heat-shock protein 25 augments radiation-induced cell-cycle arrest in murine L929 cells.
OBJECTIVE
Protective effect of small heat-shock protein (sHSP) against gamma-radiation, which associated with HSP25-induced cell-cycle delay and Bcl-2 induction. We further extended our studies on the possible role of HSP25 on ionizing radiation-induced cell-cycle regulation.


METHODS
Flow-cytometric analyses were performed for cell-cycle distribution and Western blotting. Kinase or immunocomplex kinase assay were performed for detection of cell-cycle protein expression or activation.


RESULTS
Pronounced arrest of G1, S and G2/M phase was observed by 4Gy radiation and these arrests were augmented by hsp25 overexpression. Inhibition of cyclin-D1, and cyclin-E and induction of p21Waf by radiation, which was more pronounced in hsp25 overexpressed cells than control cells, which is associated with increased binding activity of CDK2. S-phase regulator, cyclin-A and its associated CDK2 and CDC2 kinase activities were also increased by irradiation and hsp25 overexpression attenuated these phenomena. In addition, cyclin-B1 expression and its associated kinase activity, which are responsible for the transition of G2 to M phase, were increased by radiation and hsp25 overexpression also decreased these phenomena.


CONCLUSIONS
HSP25 augmented radiation-induced cell-cycle arrest (G1, S, and G2/M phase) may be caused by the HSP25-mediated cell-growth delay and is associated with radioresistance.
Laboratory of Radiation Effect, Korea Cancer Center Hospital, Seoul.
H N
HN
Cho
S J
SJ
Lee
S H
SH
Park
Y J
YJ
Lee
C K
CK
Cho
Y S
YS
Lee
D000818:Animals; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000378:metabolism; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000528:radiation effects*; D019925:Cyclin A / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D019938:Cyclin D1 / Q000037:antagonists & inhibitors; D019927:Cyclin E / Q000037:antagonists & inhibitors; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis; D016213:Cyclins / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D006360:Heat-Shock Proteins; D051379:Mice; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D010770:Phosphotransferases / Q000378:metabolism; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis; D011839:Radiation, Ionizing; D013997:Time Factors; D014407:Tumor Cells, Cultured
C534700:Ccnb1 protein, mouse; C493957:Cdkn1a protein, mouse; D019925:Cyclin A; D019926:Cyclin B; D056744:Cyclin B1; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D006360:Heat-Shock Proteins; C486113:Hsbp1 protein, mouse; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D019938:Cyclin D1; D010770:Phosphotransferases; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases