We are presently trying to test the validity of this step-wise model for chromatin remodelling during transcription by a combination of genetic and biochemical approaches. Mutations in the HAT domain that result in a significant reduction of acetyltransferase activity in vitro also severely compromise the activity of Elp3 in the elongator complex in vivo. HAT's in vivo in yeast. A step-wise model for chromatin remodelling. A transcriptional activator recruits chromatin-remodelling complexes to a promoter.
Remodelling makes it possible to assemble the pre-initiation complex and initiate transcription.
The elongator complex is loaded on the polymerase and assist in chromatin disruption during transcriptional elongation. As expected for a factor associated with elongating polymerase, the encoded protein is very abundant in HeLa cell extracts and we are purifying the elongator complex from this source as well. With the mammalian gene in hand, we have also initiated a project to delete the gene in mice. A mouse knock-out model to study elongator function might prove very informative, especially in light of the fact that a couple of recently identified elongation factors are connected to human cancer. Another possible outcome of the knock-out experiment is that elongator will prove to be essential for development, perhaps being required for 'turning on' previously silenced genes in a timely manner.