(The) role of promyelocytic leukemia zinc finger (PLZF) protein in the regulation of Ras/MAPK cascades

Abstract

The PLZF (promyelocytic leukemia zinc finger) gene was first identified as being fused to the retinoic acid receptor alpha (RARα) gene through a t(11;17)(q23;q21) translocation in a patient with acute promyelocytic leukemia and the PLZF protein has been known as a Kruppel-like transcription suppressor. To investigate the biological role of PLZF other than the role in transcription regulation, we cloned the full length PLZF gene encoding 673 amino acids and the partial cDNA in which BTB (Broad-Complex, Tramtrack, and Bric $&agrave:$brac)/POZ (poxvirus and zinc finger) domain was omitted. The 120 amino acid BTB/POZ domain is found at N-terminus of the protein and mediates dimerization. To examine the role of PLZF in vivo, we generated transgenic fly carrying the PLZF gene, which was subcloned in pUAST vector. When PLZF was mis-expressed in Drosophila eye or wing using GAL4-UAS modular expression system, major deformities, such as disordered rough eye, increased number of photoreceptors, scattered arrangement of photoreceptors and additional veins in wings, were observed. These phenotypes were consistent with those induced by enhanced MAP kinase cascade. These results show that the PLZF has the possibility in regulating MAP kinase cascade. To confirm this possibility, we crossed the transgenic flies harboring UAS-PLZF and an appropriate driver (MS1096-GAL4 or gmr-GAL4) with hypomorps or amorph in which the activity of Ras pathway components was reduced or diminished. When the transgenic flies mis-expressing PLZF were crossed with $phl^12$, hypomorph of phl (Raf ortholog), the phenotypes of the progenies harboring both parental genes were not different from those of flies mis-expressing PLZF. In other words, the rough eye phenotype of the flies mis-expressing PLZF did not affected by hypomorphic mutation at phl. However, in the case of Dsor1LH110, amorph of Dsor1 (MEK, MAPK kinase ortholog), rl1, hypomorph of rl (ERK ortholog), which are downstream of phl, the...