Serum-independent phosphorylation of c-Jun and alterations in AP-1 components by transformation with various oncogenes.
To understand the mechanisms regulating the transactivating activity of Jun/AP-1, we analyzed alterations in c-Jun induced by growth stimulation and cell transformation. Serum stimulation of quiescent NIH3T3 cells induced a marked increase in phosphorylation of c-Jun in its amino-terminal activation domain. On the other hand, this domain was highly phosphorylated, in a serum-independent manner, in cells transformed with various oncogenes, including active c-raf-1, v-src, active Ha-ras, and active erbB-2. There were no obvious differences in the phosphorylation states of c-Jun in exponentially growing normal and transformed cells. However, in the exponentially growing state, the TRECAT activity in transformed cells was markedly higher than that in normal cells. Gel retardation analysis indicated that the AP-1 components in transformed cells were significantly different from those in normal cells. These results suggest that some other alterations besides phosphorylation of c-Jun are involved in enhancement of AP-1 activity in exponentially growing transformed cells.
Kamada
S
S
Department of Oncogene Research, Osaka University, Japan.
Toyoshima
K
K
Akiyama
T
T
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D002455:Cell Division; D002471:Cell Transformation, Neoplastic; D015972:Gene Expression Regulation, Neoplastic; D011905:Genes, ras; D016391:Genes, src; D051379:Mice; D008969:Molecular Sequence Data; D009857:Oncogenes; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D016755:Proto-Oncogene Proteins c-jun / Q000737:chemistry / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D015533:Transcriptional Activation
D010750:Phosphoproteins; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger