Increased exchange rate of histone H1 on chromatin by exogenous myogenin expression.

To explore the molecular mechanism of chromatin remodeling involved in the regulation of transcriptional activation of specific genes by a myogenic regulatory factor Myogenin, we used NIH3T3 fibroblasts with a stably integrated H1.1-GFP fusion protein to monitor histone H1 movement directly by fluorescence recovery after photobleaching (FRAP) in living cells. The observation from FRAP experiments with myogenin transfected fibroblasts showed that the exchange rate of histone H1 in chromatin was obviously increased, indicating that forced expression of exogenous Myogenin can induce chromatin remodeling. The hyperacetylation of histones H3 and H4 from myogenin transfected fibroblasts was detected by triton-acid-urea (TAU)/SDS (2-D) electrophoresis and Western blot with specific antibodies against acetylated N-termini of histones H3 and H4. RT-PCR analysis indicated that the nAChR alpha-subunit gene was expressed in the transfected fibroblasts. These results suggest that the expression of exogenous Myogenin can induce chromatin remodeling and activate the transcription of Myogenin-targeted gene in non-muscle cells.