Interaction of the regulatory subunit of the cAMP-dependent protein kinase with PATZ1 (ZNF278)

The effects of cAMP in cell are predominantly mediated by the cAMP-dependent protein kinase (PKA), which is composed of two genetically distinct subunits, catalytic (C) and regulatory (R), forming a tetrameric holoenzyme R2C2. The only known function for the R subunit is that of inhibiting the activity of the C subunit kinase. It has been shown that overexpression of RI alpha, but not the C subunit kinase, is associated with neoplastic transformation. In addition, it has also been demonstrated that mutation in the RI alpha, but not the C subunit is associated with increased resistance to the DNA-damaging anticancer drug cisplatin, thus suggesting that the RI alpha subunit of PKA may have functions independent of the kinase. We show here that the RI alpha subunit interacts with a BTB/POZ domain zinc-finger transcription factor, PATZ1 (ZNF278), and co-expression with RI alpha results in its sequestration in the cytoplasm. The cytoplasmic/nuclear translocation is inducible by cAMP. C-terminus deletion abolishes PATZ1 interaction with RI alpha and results in its localization in the nucleus. PATZ1 transactivates the cMyc promoter and the presence of cAMP and co-expression with RI alpha modulates its transactivation. Moreover, PATZ1 is aberrantly expressed in cancer. Taken together, Our results showed a potentially novel mechanism of cAMP signaling mediated through the interaction of RI alpha with PATZ1 that is independent of the kinase activity of PKA, and the aberrant expression of PATZ1 in cancer point to its role in cell growth regulation. (C) 2009 Elsevier Inc. All rights reserved.