Steroid-selective initiation of chromatin remodeling and transcriptional activation of the mouse mammary tumor virus promoter is controlled by the site of promoter integration

The mouse mammary tumor virus (MMTV) promoter has target sequences recogniz ed by several steroid receptors. We present evidence for a novel mechanism that confers hormone specificity to this promoter. We show that remodeling of MMTV chromatin and the concomitant activation of the MMTV promoter are i nduced equally by glucocorticoids and progestins in one chromosomal context but are selective for glucocorticoids in another. Furthermore, increased h istone acetylation modulates MMTV promoter regulation disparately at the tw o chromosomal locations. Together, these data indicate that chromosomal arc hitecture commands a crucial role in gene regulation, imposing locus specif ic selectivity between regulators with similar sequence recognition.