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|Session Title: Cell Fate Specification - Embryo Session Type: Poster|
|Session Location: Pauley Pavilion Session Time: Sunday - Tuesday|
|Poster Board Number: 1105C Presentation Time: TUE, June 28, 2005, 3:00-4:30PM|
|Keywords: KW29 - Embryogenesis: cell fate|
Studies of Interactions between PAR Proteins. Jin
Li1, Tak-Jun Hung2, Donato Aceto1, Shinya
Aono3, Melissa Beers1, Kenneth J
Kemphues1. 1) Dept Molecular Biol & Genetics, Cornell
Univ, Ithaca, NY; 2) Union Biometrica,Somerville, MA; 3) Department of
Morphoregulaltion, Institute for Frontier Medical Sciences, Kyoto Univ,
The par genes (partitioning defective) are essential for establishment of embryonic polarity in C.elegans. Among them, PAR-3, PAR-6 and PKC-3 have a close relationship. Mutations in par-3, par-6 and pkc-3 RNAi give similar polarity defects in C.elegans early embryos. Immunostaining showed that these three proteins have very similar localization pattern. In addition, their polarized localization at the cell cortex is interdependent.
Biochemistry experiments showed that Drosophila and mammalian homologues of these three proteins directly interact with each other.
We have verified that these same biochemical interactions take place in C. elegans and are in the process of dissecting the role of each in vivo. By yeast two-hybrid and GST pull-down experiments, we found that the PAR-6 PDZ domain interacts with the PAR-3 PDZ1 domain and there is a direct association between PAR-6 N-terminal region and the PKC-3 PB1 domain. PKC-3 can bind to and phosphorylate PAR-3. Now, we are trying to verify the in vivo interactions between these three proteins, further narrow down the region that is required for each interaction and then find out the function of these interactions. We have found that the interaction between PAR-6 and PKC-3 is important for PAR-6 cortical localization.
Immunostaining at anterior par mutant backgrounds suggests that the anterior PAR complex can regulate PAR-1 posterior cortical localization. Taken together with evidence from mammalian cells and Xenopus embryos, it is possible that PKC-3 can phosphorylate PAR-1, generating a 14-3-3 binding site. Subsequently, PAR-5 (a 14-3-3 protein) can bind to and sequester anterior PAR-1 in the cytoplasm. Thus PAR-1 is restricted to the posterior cortex. Currently, we are testing this hypothesis.
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