Ribonuclease P (RNase P) is an essential Mg2+-dependent endoribonuclease, involved in tRNAbiogenesis via endonucleolytic cleavage of their 5΄-end. RNase P activity has been detected innuclei,   mitochondria   and   chloroplasts   and   although  it  is  found   in   all  kingdoms   of   life,   it1
demonstrates great variability in sequence and subunit composition. RNase P in almost all casesis a ribozyme that has focused great research interest due to the development of RNase P-basedtools able to be used in gene therapy. Regarding both the vital importance of RNase P and the thepivotal role lymphocytes play for an effective immune system we focused on the distribution andthe potential physiological role of RNase P in peripheral human lymphocytes. Herein we reportthe partial purification of RNase P activity from peripheral human lymphocytes and the effect ofnatural   and   synthetic   retinoids   (all-trans  retinoic   acid,   acitretin)   on   its   activity.  pH   andtemperature optima were found to be 7.5 and 37oC respectively. The enzyme shows optimalactivity in the presence of 70 mM NH4Cl and 5 mM MgCl2. All-trans retinoic acid and acitretinrevealed a dose-dependent inhibition on RNase P activity indicating that they may have a directeffect   on   tRNA   biogenesis.   The   ultimate   goal   of   our   approach   is   to  study   the   possibleinvolvement   of   this   ribozyme   in   the   pathogenetic   mechanisms   of   diverse   autoimmune,inflammatory and neoplastic cutaneous disorders and facilitate the further development of RNaseP-based technology for gene therapy of infectious and neoplastic dermatoses.

Retinoids as efficient inhibitors of human RNase P