Cyclin A transcriptional suppression is the major mechanism mediating homocysteine-induced endothelial cell growth inhibition.
Previously, it was reported that homocysteine (Hcy) specifically inhibits the growth of endothelial cells (ECs), suppresses Ras/mitogen-activated protein (MAP) signaling, and arrests cell growth at the G(1)/S transition of the cell cycle. The present study investigated the molecular mechanisms underlying this cell-cycle effect. Results showed that clinically relevant concentrations (50 microM) of Hcy significantly inhibited the expression of cyclin A messenger RNA (mRNA) in ECs in a dose- and time-dependent manner. G(1)/S-associated molecules that might account for this block were not changed, because Hcy did not affect mRNA and protein expression of cyclin D1 and cyclin E. Cyclin D1- and E-associated kinase activities were unchanged. In contrast, cyclin A-associated kinase activity and CDK2 kinase activity were markedly suppressed. Nuclear run-on assay demonstrated that Hcy decreased the transcription rate of the cyclin A gene but had no effect on the half-life of cyclin A mRNA. In transient transfection experiments, Hcy significantly inhibited cyclin A promoter activity in endothelial cells, but not in vascular smooth muscle cells. Finally, adenovirus-transduced cyclin A expression restored EC growth inhibition and overcame the S phase block imposed by Hcy. Taken together, these findings indicate that cyclin A is a critical functional target of Hcy-mediated EC growth inhibition.
Wang
Hong
H
Department of Medicine, Baylor College of Medicine, 2002 Holcombe Ave 109-129, Houston, TX 77030, USA. hongw@bcm.tmc.edu
Jiang
XiaoHua
X
Yang
Fan
F
Chapman
Gary B
GB
Durante
William
W
Sibinga
Nicholas E S
NE
Schafer
Andrew I
AI
D000818:Animals; D001011:Aorta / Q000166:cytology; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D019925:Cyclin A / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects* / Q000235:genetics; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects; D006710:Homocysteine / Q000494:pharmacology* / Q000502:physiology; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis / Q000187:drug effects; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects; D014471:Umbilical Veins / Q000166:cytology
D019925:Cyclin A; D012333:RNA, Messenger; D006710:Homocysteine