Cloning, expression and functional role of XrpFI alpha and beta subunits in Xenopus laevis oocyte.

The cDNAs coding for the alpha and beta components of XrpFI, an activator of ribosomal protein genes transcription, were isolated. RNA analysis showed that transcripts of the beta genes are present at constant level throughout Xenopus development unlike the beta proteins which are undetectable in the early stages of embryogenesis when transcription is silent. On the contrary, alpha transcripts and proteins were found in all the embryo stages examined. The role of the XrpFI alpha and beta subunits in rp-gene transcription has been studied by mRNA microinjection into X.laevis oocytes. The presence of the beta subunit appears to be critical for the proper rp-gene promoter function.