Structural and functional conservation of transcriptional domains in mammalian FKHR family proteins.

(A) Schematic diagram showing the conserved domains and sequence alignments of mammalian FKHR family proteins and their C elegans ortholog Daf-16. CR3 is highly acidic and conserved in all mammalian and nematode orthologs. CR2 consists of 3 conserved helical structures, which are absent in Daf-16. Dark and light shadings represent identical residues and conserved residues, respectively. S and T represent the conserved serine and threonine phosphorylation residues, respectively. H indicates the minimal predicted α helical secondary structures conserved in all mammalian homologs. (B) Transient transfection assays. Schematic diagram (left) illustrates the conserved general structure of mammalian FKHR family proteins. Arrow indicates the site of fusion with MLL. Solid horizontal black lines indicate portions of FKHR or FKHRL1 fused to the Gal4-DBD for transactivation assays. Broken horizontal line indicates the full-length Daf-16a1 fusion with Gal4-DBD. Gal4-AF10 encodes the AF10 sequence (amino acids 682-1085) present in MLL-AF10. Normalized luciferase values are shown (right) for the average of 3 experiments using a reporter gene under control of the HSV-TK promoter. Similar results were obtained on reporter constructs containing the adenoviral E1b or myelomonocytic growth factor receptor promoters (not shown). Comparable expression levels of the Gal4 constructs were confirmed by Western blot analysis (data not shown).