Inhibition of proliferation and apoptosis by the transcriptional repressor Mad1. Repression of Fas-induced caspase-8 activation.
Mad1 is a member of the Myc/Max/Mad network of transcriptional regulators that play a central role in the control of cellular behavior. Mad proteins are thought to antagonize Myc functions at least in part by repressing gene transcription. To systematically examine the function of Mad1 in growth control and during apoptosis, we have generated U2OS cell clones that express Mad1 under a tetracyline-regulatable promoter (UTA-Mad1). Mad1 was induced rapidly and efficiently, localized to the nucleus, and bound to DNA as a heterodimer with Max. The induction of Mad1 reduced cellular growth and, more profoundly, inhibited colony formation of UTA-Mad1 cells. Conditioned medium neutralized this inhibitory effect implying that Mad1 function is regulated by extracellular signals. In addition Mad1 interfered with Fas-, TRAIL-, and UV-induced apoptosis, which coincided with a reduced activation of caspase-8 during Fas-mediated apoptosis in response to Mad1 expression. Furthermore, microinjection of Mad1-expressing plasmids into fibroblasts inhibited apoptosis induced by the oncoproteins c-Myc and E1A. Thus, Mad1 not only interferes with cellular proliferation but also with apoptosis, which defines a novel aspect of Mad1 function.
Gehring
S
S
Institut für Molekularbiologie, Medizinische Hochschule Hannover, Carl-Neuberg Strasse 1, 30623 Hannover, Germany.
Rottmann
S
S
Menkel
A R
AR
Mertsching
J
J
Krippner-Heidenreich
A
A
Lüscher
B
B
D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000502:physiology* / Q000528:radiation effects; D051017:Apoptosis Regulatory Proteins; D019556:COS Cells; D002352:Carrier Proteins; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000235:genetics*; D002449:Cell Aggregation; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000502:physiology* / Q000528:radiation effects; D002460:Cell Line; D005347:Fibroblasts; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008562:Membrane Glycoproteins / Q000502:physiology; D051379:Mice; D009687:Nuclear Proteins; D009857:Oncogenes; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand; D013752:Tetracycline / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D014466:Ultraviolet Rays; D019014:fas Receptor / Q000502:physiology*
D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C501384:MAD1L1 protein, human; C501385:Mad1l1 protein, mouse; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; C505654:Tnfsf10 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D013752:Tetracycline