Forced homo-oligomerization of RARalpha leads to transformation of primary hematopoietic cells.

Almost 100% of APL patients carry chimeric transcripts encoding truncated RARalpha fused to homo-oligomerization domains from partner proteins. To gain further insights into the cellular transformation mechanisms mediated by RARalpha fusion proteins, thorough structure/function analyses have been performed and identified the POZ homo-oligomerization domain as the minimal transformation domain that is necessary and sufficient for PLZF-RARalpha-mediated in vitro transformation of primary hematopoietic cells. A transformation-incompetent PLZF-RARalpha mutant defective in homo-oligomerization but not corepressor interaction could be rescued by synthetic FKBP-oligomerization domains. Furthermore, an artificial FKBP-RARalpha construct not only mimicked various biochemical properties of bona fide RARalpha fusion proteins but also mediated an ATRA-dependent transformation. Taken together, these findings endorse an oligomerization-dependent mechanism for RARalpha-mediated transformation and suggest a potential avenue for molecular therapy.