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'-CATG(m)CG-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.