Component of the sequence-specific heterotrimeric transcription factor (NF-Y) which specifically recognizes a 5'-CCAAT-3' box motif found in the promoters of its target genes. NF-Y can function as both an activator and a repressor, depending on its interacting cofactors. NF-YA positively regulates the transcription of the core clock component ARNTL/BMAL1. Heterotrimeric transcription factor composed of three components, NF-YA, NF-YB and NF-YC. NF-YB and NF-YC must interact and dimerize for NF-YA association and DNA binding. Interacts with SP1; the interaction is inhibited by glycosylation of SP1. Interacts with ZHX1. Interacts (via N-terminus) with ZHX2 (via homeobox domain). Interacts with ZFX3. Belongs to the NFYA/HAP2 subunit family.