c-Myc regulates the coordinated transcription of brain disease-related PDCD10–SERPINI1 bidirectional gene pair

Two brain disease-related genes, one coding for the protease inhibitor SERPINI1 which is down-regulated in brain tumors, and the other for the PDCD10 programmed cell death gene which is often mutated in cerebral cavernous malformation, are closely adjacent in a head-to-head configuration and separated by only 851 bp on human chromosome 3q26. The 851-bp intergenic region contains a GC-rich 175-bp minimal bidirectional promoter which is essential for transcriptional activation of the two flanking genes. The oncogenic c-Myc transcription factor was identified to bind to a non-canonical E-box element (5′-CATGCG-3′) of the minimal bidirectional promoter to drive both gene expressions. Methylation at the specific C nucleotide within the E-box sequence (5′-CATGmCG-3′), however, would severely interfere with the binding of c-Myc to the E-box. These results suggest that c-Myc plays an important role in regulating the coordinated transcription of the PDCD10–SERPINI1 bidirectional gene pair, and is possibly involved in differential expressions of these two neighboring genes in central nervous system diseases such as brain cancer.