Transformation-specific pattern of phosphorylation of c-Jun, Jun-B, Jun-D and Egr-1 in v-sis transformed cells.
The degree of phosphorylation of c-Jun, Jun-B, Jun-D and Egr-1 transcription factors was examined during normal growth and during a prolonged period of defined transformation of NIH-3T3 cells which conditionally express v-sis [Mercola, D. et al. (1992) Oncogene, 7, 1793-1803]. During the asynchronous growth of normal cells phosphorylation of all factors was low and constant at all stages of growth from low density (c. 25 x 10(3) cells/cm2) through log-phase of growth to saturation density (c. 100 x 10(3) cells/cm2). Upon induction of v-sis, a marked and coordinate increase in phosphorylation occurred for c-Jun, Jun-B and Egr-1 to approximately 320%, 230% and 420% respectively above basal levels which was stable for the 2.5 day transformation period. The phosphorylation of Jun-D increased to over 600% and, after about 20 h, steadily declined to near basal levels at 54 h post-induction. Moreover, at any time phosphorylation and v-sis expression were fully reversible upon removal of the inducer. It appears that increased phosphorylation of the Jun family members and Egr-1 is not necessary for normal growth of NIH-3T3 but is dependent upon the expression of v-sis. Thus, normal and transformed cells may be distinguished. For c-Jun, the v-sis enhanced phosphorylation occurs at serines 63 and 73 and is required for transformation by several oncogenes [Smeal, T. et al. (1992) Mol. Cell. Biol., 12, 3507-3513]. The results described here show that the phosphorylation of additional factors is a stable and specific correlate of transformation which have have regulatory significance during transformation.
Grover-Bardwick
A
A
San Diego Regional Cancer Center, CA 92161.
Adamson
E
E
Mercola
D
D
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D002453:Cell Cycle; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D006801:Humans; D017874:Immediate-Early Proteins; D051379:Mice; D008969:Molecular Sequence Data; D020575:Oncogene Proteins v-sis; D009857:Oncogenes; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D015682:Retroviridae Proteins, Oncogenic / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D017874:Immediate-Early Proteins; D020575:Oncogene Proteins v-sis; D010982:Platelet-Derived Growth Factor; D016755:Proto-Oncogene Proteins c-jun; D015682:Retroviridae Proteins, Oncogenic; D014157:Transcription Factors