In Saccharomyces cerevisiae, a group of more than 200 co-regulated genes (Ribi 
genes) is involved in ribosome biogenesis. This regulon has recently been shown 
to rely on a small set of transcriptional regulators (mainly Abf1, but also 
Reb1, Tbf1 and Rap1) previously referred to as general regulatory factors (GRFs) 
because of their widespread binding and action at many promoters and other 
specialized genomic regions. Intriguingly, Abf1 binding to Ribi genes is 
differentially modulated in response to distinct nutrition signaling pathways. 
Such a dynamic promoter association has the potential to orchestrate both 
activation and repression of Ribi genes in synergy with neighboring regulatory 
sites and through the functional interplay of histone acetyltransferases and 
deacetylases.