Multiple NF-Y-binding CCAAT boxes are essential for transcriptional regulation of the human C7orf24 gene, a novel tumor-associated gene.

Human chromosome 7 ORF 24 (C7orf24) has been identified as a tumor-related protein, and shown to be a γ-glutamyl cyclotransferase. In the current study, we characterized the promoter region of the human C7orf24 gene to explore the transcriptional regulation of the gene. We revealed that the human C7orf24 promoter is a TATA-less promoter, containing five CCAAT boxes aligned in a forward orientation. By performing a luciferase reporter assay with 5'-deleted and site-directed mutated constructs in HeLa, MCF-7 and IMR-90 cells, we found that three proximal CCAAT boxes are important for basal transcription. Electrophoretic mobility gel shift assay and chromatin immunoprecipitation assay demonstrated that NF-Y specifically bound to all three CCAAT boxes. In addition, the mRNA and protein expression levels of C7orf24 were significantly reduced in HeLa cells depleted of NF-YB, a subunit of NF-Y. These results suggested that NF-Ys bound to the three proximal CCAAT boxes play a central role in the transcription of the gene. Furthermore, as in the case of other genes transcribed under the control of multiple NF-Ys, such as human E2f1 and cyclin b1, the C7orf24 gene expression profile oscillated during the cell cycle, implying that C7orf24 is a novel cell cycle-associated gene.