Transcription of the Pol b gene is upregulated by the phosphorylated transcription factor CREB-1 in response to alkylating agent exposure. This upregulation requires the presence of the specific cAMP response element (CRE) in the promoter of the Pol b gene (9, 10) . It has also been shown that the Pol b promoter contains a binding site for the transcription factor SP1 (11) . Although regulation at the transcription level is apparent, expression of the Pol b transcripts might also be controlled at the posttranscriptional level. In rat cells there are two alternatively polyadenylated Pol b transcripts, with 3 0 UTRs of significantly different lengths (12) . The expression of the two transcripts is tissue specific. The short transcript is present in most tissues, with significantly higher expression in testis, while the long transcript is expressed mostly in the brain and lungs (13) . Motifs present in the 3 0 UTRs of the two transcripts are likely to be responsible for regulation of tissue-specific expression.