Caenorhabditis elegans lin-45 raf is essential for larval viability, fertility and the induction of vulval cell fates.
The protein kinase Raf is an important signaling protein. Raf activation is initiated by an interaction with GTP-bound Ras, and Raf functions in signal transmission by phosphorylating and activating a mitogen-activated protein (MAP) kinase kinase named MEK. We identified 13 mutations in the Caenorhabditis elegans lin-45 raf gene by screening for hermaphrodites with abnormal vulval formation or germline function. Weak, intermediate, and strong loss-of-function or null mutations were isolated. The phenotype caused by the most severe mutations demonstrates that lin-45 is essential for larval viability, fertility, and the induction of vulval cell fates. The lin-45(null) phenotype is similar to the mek-2(null) and mpk-1(null) phenotypes, indicating that LIN-45, MEK-2, and MPK-1 ERK MAP kinase function in a predominantly linear signaling pathway. The lin-45 alleles include three missense mutations that affect the Ras-binding domain, three missense mutations that affect the protein kinase domain, two missense mutations that affect the C-terminal 14-3-3 binding domain, three nonsense mutations, and one small deletion. The analysis of the missense mutations indicates that Ras binding, 14-3-3-binding, and protein kinase activity are necessary for full Raf function and suggests that a 14-3-3 protein positively regulates Raf-mediated signaling during C. elegans development.
Hsu
Virginia
V
Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Zobel
Cheri L
CL
Lambie
Eric J
EJ
Schedl
Tim
T
Kornfeld
Kerry
K
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000502:physiology*; D005260:Female; D005298:Fertility / Q000235:genetics / Q000502:physiology; D005804:Genes, Lethal; D007814:Larva / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D010641:Phenotype; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D016415:Sequence Alignment; D013489:Suppression, Genetic; D048490:raf Kinases
D029742:Caenorhabditis elegans Proteins; D017346:Protein Serine-Threonine Kinases; C454817:lin-45 protein, C elegans; D048490:raf Kinases