Transactivation of Fra-1 and consequent activation of AP-1 occur extracellular signal-regulated kinase dependently.
Mitogen-activated protein (MAP) kinase, extracellular-signal-regulated kinases (ERKs) play an important role in activating AP-1-dependent transcription. Studies using the JB6 mouse epidermal model and a transgenic mouse model have established a requirement for AP-1-dependent transcription in tumor promotion. Tumor promoters such as 12-O-tetradecanoylphorbol-13-acetate (TPA) and epidermal growth factor induce activator protein 1 (AP-1) activity and neoplastic transformation in JB6 transformation-sensitive (P(+)) cells, but not in transformation-resistant (P(-)) variants. The resistance in one of the P(-) variants can be attributed to the low levels of the MAP kinases, ERKs 1 and 2, and consequent nonresponsiveness to AP-1 activation. The resistant variant is not deficient in c-fos transcription. The purpose of these studies was to define the targets of activated ERK that lead to AP-1 transactivation. The results establish that the transactivation domain of Fra-1 can be activated, that activation of Fra-1 is ERK dependent, and that a putative ERK phosphorylation site must be intact for activation to occur. Fra-1 was activated by TPA in ERK-sufficient P(+) cells but not in ERK-deficient P(-) cells. A similar activation pattern was seen for c-Fos but not for Fra-2. Gel shift analysis identified Fra-1 as distinguishing mitogen-activated (P(+)) from nonactivated (P(-)) AP-1 complexes. A second AP-1-nonresponsive P(-) variant that underexpresses Fra-1 gained AP-1 response upon introduction of a Fra-1 expression construct. These observations suggest that ERK-dependent activation of Fra-1 is required for AP-1 transactivation in JB6 cells.
Young
Matthew R
MR
Basic Research Laboratory, National Cancer Institute-Frederick. Intramural Research Support Program, Science Applications International Corporation-Frederick, Frederick, Maryland 21702, USA. youngm@ncifcrf.gov
Nair
Rajalakshmi
R
Bucheimer
Natalie
N
Tulsian
Preety
P
Brown
Nicole
N
Chapp
Cristi
C
Hsu
Tin-Chen
TC
Colburn
Nancy H
NH
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002273:Carcinogens / Q000633:toxicity; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D016762:Genes, fos; D014644:Genetic Variation; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D017434:Protein Structure, Tertiary; D016760:Proto-Oncogene Proteins c-fos / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D000099169:Fos-Related Antigen 1
D002273:Carcinogens; D020928:Mitogen-Activated Protein Kinases; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D013755:Tetradecanoylphorbol Acetate; D018808:Transcription Factor AP-1; D000099169:Fos-Related Antigen 1