Regulation of thymosin beta 4 mRNA levels during cell proliferation.
The levels of thymosin beta 4 mRNA were studied throughout the cell cycle of NIH 3T3 cells. In serum deprived, quiescent cells, the levels of thymosin beta 4 were undetectable; after serum restoration, the cells were induced to proliferate and we found a pronounced increase in thymosin beta 4 mRNA levels at the G1/S transition. Thymosin beta 4 mRNA was induced even in the presence of cycloheximide. On the other hand, cycling cells that were synchronized at different stages of the cycle by means of mitotic shake-off after nocodazole arrest or a double thymidine block did not show any variation in the levels of thymosin beta 4 mRNA when they progressed synchronously through the cycle. In conclusion, the present data indicate that the thymosin beta 4 gene is regulated by cell proliferation but it is not a cell cycle-regulated gene. Finally, we studied thymosin beta 4 mRNA stability by inhibiting thymosin beta 4 gene transcription with actinomycin D. Our results suggest that thymosin beta 4 mRNA has a pronounced stability, a fact that might be relevant to account for the presence of thymosin beta 4 in enucleated cells like platelets.
Zalvide
J B
JB
Departamento de Fisiologia, Laboratorio de Neurociencias Ramon Dominguez, Facultad de Medicina, Santiago de Compostela, Spain.
Alvarez
C V
CV
Vidal
A
A
Dieguez
C
C
Vega
F V
FV
Domínguez
F
F
D000818:Animals; D015152:Blotting, Northern; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism*; D016193:G1 Phase; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D008938:Mitosis / Q000187:drug effects / Q000502:physiology; D015739:Nocodazole / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics; D016196:S Phase; D013947:Thymosin / Q000096:biosynthesis / Q000235:genetics*; D000099201:Thymosin beta(4)
D003513:Cycloheximide; D003609:Dactinomycin; D015739:Nocodazole; D012333:RNA, Messenger; D013947:Thymosin; D000099201:Thymosin beta(4)