Component of the NF-Y/HAP transcription factor complex. 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 (By similarity). Interacts with NFYB2 (PubMed:18193457). Interacts with NFYB8, NFYB10 and HD5/NFYB11 (PubMed:26542958). Belongs to the NFYC/HAP5 subunit family.