An increasing number of transcription factors have been shown to activate DNA replication. However, the underlying mechanism remains to be elucidated. Here it is shown that when tethered to a cellular replication origin, the acidic transcriptional activation domain of the breast cancer protein BRCA1 alters the local chromatin structure and stimulates chromosomal DNA replication. Cancer-predisposing mutations in BRCA1 that abolish transcriptional activation also prevent chromatin remodeling and activation of replication. Chromatin remodeling occurs even in the absence of a functional replication origin. Thus, increasing chromatin accessibility may be an important mechanism used by transcription factors to facilitate multiple nuclear processes.