Transcriptional squelching re-examined

The introduction of a potent transcriptional activator into eukaryotic cells can paradoxically suppress the transcription of a co-introduced target gene. This so-called ‘squelching’ is thought to result from titration of one or more general transcription factors (GTFs), indicating that GTFs might be in limited supply within the cell,. We now find that in mammalian cells, squelching is limited to episomal target genes, whereas genes integrated into cellular chromatin are immune.