Bidirectional promoter connects the poly(ADP-ribose) polymerase 2 (PARP-2)gene to the gene for RNase P RNA - Structure and expression of the mouse PARP-2 gene

Poly(ADP-ribose) polymerase 2 (PARP-2) is a DNA damage-dependent enzyme tha t belongs to a growing family of enzymes seemingly involved in genome prote ction. To gain insight into the physiological role of PARP-2 and to investi gate mechanisms of PARP-2 gene regulation, we cloned and characterized the murine PARP-2 gene. The PARP-2 gene consists of 16 exons and 15 introns spa nning about 13 kilobase pairs. Interestingly, the PARP-2 gene lies head to head with the gene encoding the mouse RNase P RNA subunit. The distance bet ween the transcription start sites of the PARP-2 and RNase P RNA genes is 1 14 base pairs. This suggested that regulation of the expression of both gen es may be coordinated through a bi-directional promoter. The PARP-2/RNase P RNA gene organization is conserved in the human. To our knowledge, this is the first report of a RNA polymerase II gene and an RNA polymerase III gen e sharing the same promoter region and potentially the same transcriptional control elements. Reporter gene constructs showed that the 113-base pair i ntergenic region was indeed sufficient for the expression of both genes and revealed the importance of both the TATA and the DSE/Oct-1 expression cont rol elements for the PARP-2 gene transcription. The expression of both gene s is clearly independently regulated. PARP-2 is expressed only in certain t issues, and RNase P RNA is ex pressed in all tissues, This suggests that bo th genes may be subjected to multiple levels of control and may be regulate d by different factors in different cellular contexts.