Nucleosome remodelling complexes play a key role in gene activation in response 
to environmental changes by driving promoter chromatin to reach an accessible 
configuration. They also mediate genome-wide chromatin organization, although 
their role in processes other than activation-related chromatin remodelling are 
poorly understood. The Saccharomyces cerevisiae ADH2 gene represents an 
excellent model for understanding the role of chromatin structure and 
remodelling in gene regulation. Following glucose depletion, highly positioned 
promoter nucleosomes are destabilized leading to strictly regulated kinetics of 
transcriptional activation. Nevertheless, no chromatin remodelling activities 
responsible for establishing or remodelling ADH2 chromatin structure have been 
identified to date. Here we show that the absence of the Isw1 and Chd1 
ATP-dependent chromatin remodelling activities delays the maximal expression of 
ADH2 without impairing the chromatin remodelling that occurs upon activation. 
Instead, a destabilized chromatin structure on the ADH2 coding and termination 
region is observed in the absence of Isw1 or Chd1 in repressing conditions. The 
specific Isw1 complex involved in this nucleosome repositioning is Isw1b because 
the deletion of Ioc2 and Ioc4, but not of Ioc3, causes the same phenotype as the 
deletion of Isw1. Moreover, the lack of Chd1 combined with the absence of Isw1 
and Isw2 impairs nucleosome spacing along the ADH2 gene, and genome-wide in S. 
cerevisiae. Thus, the ISWI and Chd1 remodelling factors are not only involved in 
transcription-related chromatin remodelling, but also are required to maintain a 
specific chromatin configuration across the yeast genome.