Characterization of maternal and zygotic D-raf proteins: dominant negative effects on Torso signal transduction.
The maternal D-raf serine/threonine kinase acts downstream of Torso (Tor) for specification of cell fates at the embryonic termini. D-raf activity is also required in other signal transduction pathways and consistent with its pleiotropic role, we find accumulation of a 90-kD D-raf protein throughout embryonic development. We also characterize the accumulation of maternal D-raf proteins in 0-2-hr embryos derived from females with germ cells lacking D-raf activity. Accumulation of a 90-kD or truncated mutant D-raf protein is observed for some of these embryos, while others lack the maternal D-raf protein. Then to determine whether rescue of the Tor pathway is influenced by pools of nonfunctional maternal D raf. wild-type D-raf mRNA was injected into embryos that inherit maternal stores of inactive 90-kD of truncated D-raf protein. For embryos lacking the maternal D-raf protein, a high level of terminal rescue is obtained. In contrast, rescue is reduced or not observed for embryos that accumulate mutant maternal D-raf proteins. These findings suggest that mutant forms of D-raf may deplete the embryo of a positive activator and/or form inactive protein complexes that affect rescue of the Tor pathway.
Radke
K
K
Department of Zoology and Genetics, Iowa State University, Ames 50011-3260, USA.
Baek
K H
KH
Ambrosio
L
L
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics; D004330:Drosophila / Q000196:embryology / Q000235:genetics*; D029721:Drosophila Proteins; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf; D012333:RNA, Messenger; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*; D015053:Zygote
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C074090:TLL protein, Drosophila; D020794:Receptor Protein-Tyrosine Kinases; C080148:tor protein, Drosophila; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf