ABSTRACT
In RA-treated P19 cells, the level of RXRa mRNA appeaJrS to be increased, whereas that of RXR~ is unchanged, and that of RXRy is decreased unpublished results). In contrast, RXRa mRNA levels appear to be decreased by RA treatment ofthe promyelocytic leukemia cells HL60 and NB4 (188), thus suggesting a complex regulation of expression of the RXRa gene by retinoic acid. In any event, these results suggest that a subset of RAR and RXR types could control the primary response to retinoic acids.
