The DEAD box protein Ddx42p modulates the function of ASPP2, a stimulator of apoptosis.

Ddx42p is a recently characterized mammalian DEAD box protein with unknown cellular function. We found that in human cells Ddx42p physically interacts with ASPP2, a major apoptosis inducer known to enhance p53 transactivation of proapoptotic genes. The proteins interact via a domain within the carboxy-terminal part of Ddx42p and a mid-amino-terminal sequence as well as the ankyrin-SH3 region of ASPP2. Overexpression of Ddx42p interferes with apoptosis induction by ASPP2, whereas Ddx42p knockdown reduces the survival rate of cultured human cells. In addition, ASPP2 is found in cytoplasm and nucleus at low Ddx42p level, and predominantly in cytoplasm at high concentration of Ddx42p, respectively. Our results show that Ddx42p is capable of modulating ASPP2 function.