A two-hit mechanism for pre-mitotic arrest of cancer cell proliferation by a polyamide-alkylator conjugate.
A polyamide-chlorambucil conjugate (1R-Chl) arrests a wide range of human cancer cell lines at the G2/M phase of the cell cycle and downregulates histone H4c gene expression. However, an siRNA against H4c mRNA causes G1/S arrest. Here, we report that 1R-Chl downregulates H4c prior to G2/M arrest. G2/M arrest is the result of extensive DNA damage by 1R-Chl, which leads to phosphorylation of H2A.X at serine 139, recruitment of the Nbs1 repair protein, and a cascade of unknown events culminating with cdc2 phosphorylation at tyrosine 15 and abolishment of cdc2 kinase activity. A control polyamide-Chl conjugate, which neither binds to the H4c gene nor has an anti-proliferative effect by itself, causes G2/M arrest when cells are treated with siRNAs specific for H3 or H4c.
Alvarez
David
D
Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Chou
C James
CJ
Latella
Lucia
L
Zeitlin
Samantha G
SG
Ku
Sherman
S
Puri
Pier Lorenzo
PL
Dervan
Peter B
PB
Gottesfeld
Joel M
JM
D002455:Cell Division; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002699:Chlorambucil / Q000494:pharmacology* / Q000627:therapeutic use; D016195:G2 Phase; D005786:Gene Expression Regulation / Q000187:drug effects; D006657:Histones / Q000037:antagonists & inhibitors / Q000235:genetics; D006801:Humans; D007399:Interphase; D008954:Models, Biological; D009369:Neoplasms / Q000473:pathology*; D011108:Polymers / Q000494:pharmacology / Q000627:therapeutic use; D034741:RNA, Small Interfering / Q000494:pharmacology
D006657:Histones; D011108:Polymers; D034741:RNA, Small Interfering; D002699:Chlorambucil