CDP CUT IS THE DNA-BINDING SUBUNIT OF HISTONE GENE-TRANSCRIPTION FACTOR HINF-D - A MECHANISM FOR GENE-REGULATION AT THE G(1)/S PHASE CELL-CYCLE TRANSITION POINT INDEPENDENT OF TRANSCRIPTION FACTOR E2F/

Transcription of the genes for the human histone proteins H4, H3, H2A, H2B, and H1 is activated at the G(1)/S phase transition of the cell c ycle. We have previously shown that the promoter complex HiNF-D, which interacts with cell cycle control elements in multiple histone genes, contains the key cell cycle factors cyclin A, CDC2, and a retinoblast oma (pRB) protein-related protein. However, an intrinsic DNA-binding s ubunit for HINF-D was not identified. Many genes that are up-regulated at the G(1)/S phase boundary are controlled by E2F, a transcription f actor that associates with cyclin-, cyclin-dependent kinase-, and pRB- related proteins. Using gel-shift immunoassays, DNase I protection, an d oligonucleotide competition analyses, we show that the homeodomain p rotein CDP/cut, not E2F, is the DNA-binding subunit of the HiNF-D comp lex. The HINF-D (CDP/cut) complex with the H4 promoter is immunoreacti ve with antibodies against CDP/cut and pRB but not p107, whereas the C DP/cut complex with a nonhistone promoter (gp91-phox) reacts only with CDP and p107 antibodies. Thus, CDP/cut complexes at different gene pr omoters can associate with distinct pRB-related proteins. Transient co expression assays show that CDP/cut modulates H4 promoter activity via the HiNF-D binding site. Hence, DNA replication-dependent histone H4 genes are regulated by an EZF-independent mechanism involving a comple x of CDP/cut with cyclin A/CDC2/RB-related proteins.