Transcription elongation factor Brd4-P-TEFb accelerates intestinal differentiation-associated gene expression.

Background: Expression of the fructose transporter gene and histone acetylation in the transcribed region are induced by differentiation associated-signals such as glucocorticoids and p44/42 mitogen-activated protein kinase (MAPK) inhibition in small intestinal Caco-2 cells.

Methods: We co-treated with glucocorticoid receptor agonist dexamethasone (Dex) and p44/42 MAPK inhibitor PD98059 (PD) in Caco-2 cells with or without Brd4 small hairpin (sh) RNA expression vector, and the cells were analyzed by qRT-PCR and chromatin immunoprecipitation assays. The small intestine of wild-type mice and mice during weaning period were analyzed by qRT-PCR.

Results: Co-treatment with Dex and PD increased binding of the bromodomain-containing protein-4 (Brd4)-positive transcriptional elongation factor-b (P-TEFb)-RNA polymerase II complex to acetylated histones in the transcribed region of . Brd4-protein depletion by shRNA revealed that the association of these proteins on the transcribed region of promoted gene expression in a Brd4-dependent manner. Expression of small-intestine , but not another intestinal gene sucrase-isomaltase, during weaning period, was significantly lower in mice compared with wild-type mice.

Conclusions: Brd4-P-TEFb plays a crucial role in differentiation-associated transcription of gene in intestinal Caco-2 cells and in the small intestine of mice during weaning period.

General Significance: Histone acetylation and the transcription elongation factor Brd4 are important for expression in the small intestine.