Requirement of RSF and FACT for transcription of chromatin templates in vitro.

Transcription of naked DNA in vitro requires the general transcription factors and RNA polymerase II. However, this minimal set of factors is not sufficient for transcription when the DNA template is packaged into chromatin. Here, a factor that facilitates activator-dependent transcription initiation on chromatin templates was purified. This factor, remodeling and spacing factor (RSF), has adenosine triphosphate-dependent nucleosome-remodeling and spacing activities. Polymerases that initiate transcription with RSF can only extend their transcripts in the presence of FACT (facilitates chromatin transcription). Thus, the minimal factor requirements for activator-dependent transcription on chromatin templates in vitro have been defined.