Inhibition of hypoxia-inducible factor-1alpha (HIF-1alpha) protein synthesis by DNA damage inducing agents.
Hypoxia-inducible factor (HIF) is a heterodimeric transcription factor that is composed of a hypoxia-inducible alpha subunit (HIF-1alpha and HIF-2alpha) and a constitutively expressed beta subunit (HIF-1beta). HIF mediates the adaptation of cells and tissues to low oxygen concentrations. It also plays an important role in tumorigenesis and constitutes an important therapeutic target in anti-tumor therapy. We have screened a number of reported HIF inhibitors for their effects on HIF-transcriptional activity and found that the DNA damage inducing agents camptothecin and mitomycin C produced the most robust effects. Camptothecin is a reported inhibitor of HIF-1alpha translation, while mitomycin C has been reported to induce p53-dependent HIF-1alpha degradation. In this study we demonstrate that the inhibitory effect of mitomycin C on HIF-1alpha protein expression is not dependent on p53 and protein degradation, but also involves HIF-1alpha translational regulation. Initiation of a DNA damage response with the small molecule p53 activator NSC-652287 (RITA) has been reported to inhibit HIF-1alpha protein synthesis by increasing the phosphorylation of eIF2alpha. However, we show here that even when eIF2alpha phosphorylation is prevented, the DNA damage inducing drugs mitomycin C, camptothecin and NSC-652287 still inhibit HIF-1alpha protein synthesis to the same extent. The inhibitory effects of camptothecin on HIF-1alpha expression but not that of mitomycin C and NSC-652287 were dependent on cyclin-dependent kinase activity. In conclusion, specific types of DNA damage can bring about selective inhibition of HIF-1alpha protein synthesis. Further characterization of the involved mechanisms may reveal important novel therapeutic targets.
Lou
Jessica Jie Wei
JJ
Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
Chua
Yee Liu
YL
Chew
Eng Hui
EH
Gao
Jie
J
Bushell
Martin
M
Hagen
Thilo
T
D020121:5' Untranslated Regions / Q000235:genetics; D017209:Apoptosis / Q000187:drug effects; D002166:Camptothecin / Q000494:pharmacology*; D015687:Cell Hypoxia / Q000187:drug effects; D002460:Cell Line; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004249:DNA Damage; D005047:Etoposide / Q000494:pharmacology; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis* / Q000235:genetics; D016685:Mitomycin / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D020121:5' Untranslated Regions; D015852:Eukaryotic Initiation Factor-2; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016159:Tumor Suppressor Protein p53; D016685:Mitomycin; D005047:Etoposide; D018844:Cyclin-Dependent Kinases; D002166:Camptothecin