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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Gene expression during terminal differentiation: dexamethasone suppression of inducer-mediated alpha 1- and beta maj-globin gene expression.

Previous studies demonstrated that hexamethylenebisacetamide (HMBA)-mediated murine erythroleukemia cell (MELC) commitment to terminal division could be suppressed by dexamethasone. A rapid (less than 2 hr) increase (step-up) in commitment to terminal cell division was observed if, after 60-70 hr in culture with inducer and steroid, MELC were transferred to medium with HMBA alone. This step-up commitment was not inhibited by actinomycin or cordycepin but was blocked by cycloheximide. In this study, we show that dexamethasone blocks HMBA-mediated activation of alpha 1- and beta maj-globin gene transcription but not the induced chromatin change characterized by appearance of DNase I-hypersensitive regions upstream from the 5' cap sites of the alpha 1- and beta maj-globin genes. A rapid (less than 2 hr) activation (step-up) of alpha 1-globin gene transcription was observed if, after 48-60 hr in culture with HMBA and dexamethasone, MELC were transferred to medium with HMBA alone. Activation of transcription of the beta maj-globin gene requires 12-24 hr of further culture. Cycloheximide inhibits step-up transcription of both globin genes. Thus, dexamethasone blocks HMBA-mediated modulation of transcription of several nonlinked genes whose expression is altered in a coordinated manner during induced MELC terminal differentiation. Further, the steroid blocks at a late step, a step after that which is rate-limiting to HMBA-mediated MELC differentiation.[1]

References

  1. Gene expression during terminal differentiation: dexamethasone suppression of inducer-mediated alpha 1- and beta maj-globin gene expression. Kaneda, T., Murate, T., Sheffery, M., Brown, K., Rifkind, R.A., Marks, P.A. Proc. Natl. Acad. Sci. U.S.A. (1985) [Pubmed]
 
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