Many factors may affect the OFF and ON time of a gene at different timescales. Factors affecting the OFF time could include chemical modifications of the promoter and enhancer, or the displacement of the +1 nucleosome from the transcription start site. Transcription factors may prolong the ON time of a gene by stabilizing basal transcription machinery at the promoter, or enhancer-promoter contacts, for more successful re-initiation. On the other hand, a repressive transcription factor might recruit factors such as chromatin remodelers that could result in a shortening of the active period of the gene. Abbreviations: PIC, pre-initiation complex; TFIID, general transcription factor II-D; TBP, TATA binding protein; HDAC, histone deacetylase.