PRENYLATION OF RHOB IS REQUIRED FOR ITS CELL TRANSFORMING FUNCTION BUT NOT ITS ABILITY TO ACTIVATE SERUM RESPONSE ELEMENT-DEPENDENT TRANSCRIPTION

Rho regulates cytoskeletal actin structure and integrin-mediated cell adhesion. Rho also has a role in cell growth regulation and is require d for cell transformation by oncogenic Ras. Recently, it has been demo nstrated that Rho can activate transcription from the c-fos serum resp onse element (SRE). This raised the possibility that functions require d for Rho-mediated cell transformation might overlap with those involv ed in transcriptional regulation. Here we show that RhoB can activate the SRE and can synergize in cell transformation with constitutively a ctivated Raf-CAAX. Significantly, unprenylated forms of RhoB that are biologically inert and unable to transform cells can still activate SR E-dependent transcription. This finding suggests that transcriptional activation by Rho may be separable from its cell transforming function s.