The Human dsRNA binding protein PACT is unable to functionally substitute for the Drosophila dsRNA binding protein R2D2

The dsRNA binding protein (dsRBP) PACT was first described as an activator of the dsRNA dependent protein kinase PKR in response to stress signals.  Additionally, it has been identified as a component of the small RNA processing pathway.  A role for PACT in this pathway represents an important interplay between two modes of post-transcriptional gene regulation.  The function of PACT in this context is poorly understood.  Thus, additional approaches are required to clarify the mechanism by which PACT functions.  In this study, the genetic utility of  Drosophila melanogaster was employed to identify dsRNA-binding proteins that are functionally orthologous to PACT.  Transgenic  Drosophila expressing human PACT were generated to determine whether PACT is capable of functionally substituting for the  Drosophila dsRBP R2D2, which has a well-defined role in small RNA biogenesis.  Results presented here indicate that PACT is unable to substitute for R2D2 at the whole organism level.