Siah ubiquitin ligases modulate nodal signaling during zebrafish embryonic development.
Siah2 is a zebrafish homologue of mammalian Siah family. Siah acts as an E3 ubiquitin ligase that binds proteins destined for degradation. Extensive homology between siah and Drosophila Siah homologue (sina) suggests their important physiological roles during embryonic development. However, detailed functional studies of Siah in vertebrate development have not been carried out. Here we report that Siah2 specifically augments nodal related gene expression in marginal blastomeres at late blastula through early gastrula stages of zebrafish embryos. Siah2 dependent Nodal signaling augmentation is confirmed by cell-based reporter gene assays using 293T cells and 3TPluciferase reporter plasmid. We also established a molecular hierarchy of Siah as a upstream regulator of FoxH1/Fast1 transcriptional factor in Nodal signaling. Elevated expression of nodal related genes by overexpression of Siah2 was enough to override the inhibitory effects of atv and lft2 on the Nodal signaling. In particular, E3 ubiquitin ligase activity of Siah2 is critical to limit the duration and/or magnitude of Nodal signaling. Additionally, since the embryos injected with Siah morpholinos mimicked the atv overexpression phenotype at least in part, our data support a model in which Siah is involved in mesendoderm patterning via modulating Nodal signaling.
Department of Biological Sciences, College of Bioscience and Biotechnology, Chungnam National University, Daejeon 305-764, Korea.
Nami
N
Kang
Program in Genomics of Differentiation, Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA.
Minho
M
Won
Myungchull
M
Rhee
Hyunju
H
Ro
D000818:Animals; D019521:Body Patterning; D004625:Embryo, Nonmammalian / Q000201:enzymology; D047108:Embryonic Development; D051858:Forkhead Transcription Factors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D057809:HEK293 Cells; D006801:Humans; D055458:Left-Right Determination Factors / Q000502:physiology; D009687:Nuclear Proteins / Q000502:physiology*; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000502:physiology*; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000378:metabolism / Q000502:physiology; D051176:beta Catenin / Q000378:metabolism; D000098563:Seven in Absentia Proteins
D051858:Forkhead Transcription Factors; D055458:Left-Right Determination Factors; D009687:Nuclear Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; C495269:ctnnb1 protein, zebrafish; C491116:foxh1 protein, zebrafish; C117508:lft1 protein, zebrafish; D044767:Ubiquitin-Protein Ligases; D000098563:Seven in Absentia Proteins