A CRITICAL ROLE FOR CHROMATIN IN MOUNTING A SYNERGISTIC TRANSCRIPTIONAL RESPONSE TO GAL4-VP16

The role of chromatin in mounting a synergistic transcriptional respon se to GAL4-VP16 was investigated. Strong synergy was observed when chr omatin templates, were used in vitro. The synergy was severely reduced when naked DNA templates were transcribed. In vivo synergy was strong when nonreplicating templates were used. However, the use of replicat ing templates, which involved transient disruptions of chromatin, led to strong reductions in synergy. In both of these low-synergy response s, transcription levels were high. We infer that strong synergy has a requirement for chromatin that may be understood in terms of the compe tition between multiple activator molecules and histone cores for prom oter DNA.