Evidence that the C-terminal domain (CtD) autoinhibits neural repression by Drosophila E(spl)M8.
Analysis of the retinal defects of a CK2 phosphomimetic variant of E(spl)M8 (M8S(159)D) and the truncated protein M8* encoded by the E(spl)D allele, suggest that the nonphosphorylated CtD "autoinhibits" repression. We have investigated this model by testing for inhibition (in "trans") by the CtD fragment in its nonphosphorylated (M8-CtD) and phosphomimetic (M8SD-CtD) states. In N(+) flies, ectopic M8-CtD compromises lateral inhibition, i.e., elicits supernumerary bristles as with loss of N signaling. This antimorphic activity of M8-CtD strongly rescues the reduced eye and/or bristle loss phenotypes that are elicited by ectopic M8SD or wild type M8. Additionally, the severely reduced eye of N(spl)/Y; E(spl)D/+ flies is also rescued by M8-CtD. Rescue is specific to the time and place, the morphogenetic furrow, where "founding" R8 photoreceptors are specified. In contrast, the phosphomimetic M8SD-CtD that is predicted to be deficient for autoinhibition, exhibits significantly attenuated or negligible activity. These studies provide evidence that autoinhibition by the CtD regulates M8 activity in a phosphorylation-dependent manner.
Kahali
Bhaskar
B
Department of Biology, West Virginia University, Morgantown, WV, USA.
Kim
Jee-Eun
JE
Karandikar
Umesh
U
Bishop
Clifton P
CP
Bidwai
Ashok P
AP
D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D047390:Casein Kinase II / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development; D005123:Eye / Q000254:growth & development / Q000378:metabolism; D005260:Female; D018257:Helix-Loop-Helix Motifs; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D009420:Nervous System / Q000254:growth & development / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012679:Sense Organs / Q000254:growth & development / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques
D051792:Basic Helix-Loop-Helix Proteins; D047390:Casein Kinase II; D029721:Drosophila Proteins; D010455:Peptides; D012097:Repressor Proteins; C492706:E(spl)m8-HLH protein, Drosophila; C091023:gro protein, Drosophila