Transcriptional activation of Odf2/Cenexin by cell cycle arrest and the stress activated signaling pathway (JNK pathway).

The centrosome/basal body protein ODF2/Cenexin is necessary for the formation of the primary cilium. Primary cilia are essential organelles that sense and transduce environmental signals. Primary cilia are therefore critical for embryonic and postnatal development as well as for tissue homeostasis in adulthood. Impaired function of primary cilia causes severe human diseases. ODF2 deficiency prevents formation of the primary cilium and is embryonically lethal. To explore the regulation of primary cilia formation we analyzed the promoter region of Odf2 and its transcriptional activity. In cycling cells, Odf2 transcription is depressed but becomes up-regulated in quiescent cells. Low transcriptional activity is mediated by sequences located upstream from the basal promoter, and neither transcription factors with predicted binding sites in the Odf2 promoter nor Rfx3 or Foxj, which are known to control ciliary gene expression, could activate Odf2 transcription. However, co-expression of either C/EBPα, c-Jun or c-Jun and its regulator MEKK1 enhances Odf2 transcription in cycling cells. Our results provide the first analysis of transcriptional regulation of a ciliary gene. Furthermore, we suggest that transcription of even more ciliary genes is largely inhibited in cycling cells but could be activated by cell cycle arrest and by the stress signaling JNK pathway.