The histone-like NF-Y is a bifunctional transcription factor

NF-Y is a trimeric transcription factor containing H2A/H2B-like subunits, which specifically binds to the CCAAT box, a common eukaryotic promoter element. To gain insights into NF-Y-dependent transcriptional regulation, we assessed its relationships with positive histone marks by chromatin immunoprecipitation-on-chip and correlative-profiling studies. Unbiased identification of binding sites shows that the majority of genes are bound by NF-Y in the promoter and/or within the coding region. Parallel analysis of H3K9-14ac and H3K4me3 sites indicates that NF-Y loci can be divided in two distinct clusters: (i) a large cohort contains H3K9-14ac and H3K4me3 marks and correlates with expression and (ii) a sizeable group is devoid of these marks and is found on transcriptionally silent genes. Within this class, we find that NF-Y binding is associated with negative histone marks, such as H4K20me3 and H3K27me3. NF-Y removal by a dominant negative NF-YA leads to a decrease in the transcription of expressed genes associated with H3K4me3 and H3K9-14ac, while increasing the levels of many inactive genes. These data indicate that NF-Y is embedded in positive as well as in negative methyl histone marks, serving a dual function in transcriptional regulation, as an activator or as a repressor.