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Regulation of transcription factor mRNA accumulation during 3T3-L1 preadipocyte differentiation by antagonists of
J M Stephens1, M Butts, R Stone
1Department of Biochemistry, School of Medicine, East Carolina University, Greenville, NC 27858.
Abstract:
3T3-L1 preadipocytes differentiate into cells having the biochemical properties of adipocytes; tumor necrosis factor-alpha (TNF), retinoic acid (RA), and transforming growth factor-beta (TGF-beta), attenuate this process. Inhibition of differentiation by these agents, thought to be at the level of transcription, has been investigated by examining the accumulation of mRNA for six transcription factors and the autocrine growth factor interleukin 6 (IL-6). Upon induction of differentiation, a rapid and major accumulation of c-fos and jun-B mRNA was observed that returned to near basal levels within 4-6 h. In contrast, c-jun mRNA, although rapidly expressed following induction of differentiation, remained at relatively constant levels throughout the time course. Exposure of the cells to 5 nM TNF potentiated the accumulation of all 3 mRNAs but most significantly c-jun (12-fold), which remained elevated for at least 24 h after treatment. In control differentiating cells, krox-20 and fox-B were expressed transiently, 30 min to 2 h, while fra-1 mRNA accumulated over an extended period, 1 to 8 h. Again, TNF enhanced the accumulation of these mRNAs. Accumulation of mRNA for C/EBP, a transcription factor proposed to control expression of genes involved in the terminally differentiated state was attenuated after exposure of the cells to TNF. C/EBP expression was also inhibited in cells exposed to RA or TGF-beta. IL-6 mRNA was expressed briefly (30 min to 2 h) and again transiently (at 8 h after induction of differentiation). TNF treatment markedly enhanced accumulation of IL-6 message.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Tumor necrosis factor-alpha (TNF) and other factors inhibit adipocyte differentiation by altering transcription factor mRNA levels. TNF significantly increased c-jun mRNA and IL-6 mRNA accumulation.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- 3T3-L1 preadipocytes can differentiate into adipocytes.
- Tumor necrosis factor-alpha (TNF), retinoic acid (RA), and transforming growth factor-beta (TGF-beta) inhibit this differentiation process.
- This inhibition is thought to occur at the transcriptional level.
Purpose of the Study:
- To investigate the transcriptional regulation of adipocyte differentiation.
- To examine the effects of TNF, RA, and TGF-beta on the mRNA accumulation of key transcription factors and interleukin-6 (IL-6).
Main Methods:
- 3T3-L1 preadipocytes were induced to differentiate.
- Cells were treated with TNF, RA, or TGF-beta.
- mRNA levels for transcription factors (c-fos, jun-B, c-jun, krox-20, fox-B, fra-1, C/EBP) and IL-6 were measured using techniques such as Northern blotting (implied).
Main Results:
- Differentiation induction led to rapid c-fos and jun-B mRNA accumulation.
- TNF treatment potentiated c-jun and IL-6 mRNA accumulation significantly.
- TNF, RA, and TGF-beta attenuated the accumulation of C/EBP mRNA, a key factor in terminal differentiation.
Conclusions:
- TNF, RA, and TGF-beta interfere with adipocyte differentiation at the transcriptional level.
- TNF modulates the expression of multiple transcription factors and IL-6 during differentiation.
- C/EBP expression is a critical target for inhibition by these factors.