Ubiquitination and Degradation of the Zebrafish Paired‐Like Homeobox Protein Vsx‐1

• Published in: Journal of neurochemistry Vol. 75; no. 1; pp. 48 - 55
• Main Authors: Kurtzman, Aaron L., Gregori, Luisa, Haas, Arthur L., Schechter, Nisson
• Format: Journal Article
• Language: English
• Published: Oxford UK Blackwell Science Ltd 01.07.2000; Blackwell
• Subjects: 26S proteasome; Adenosine Triphosphatases - metabolism; Animals; Biological and medical sciences; Bipolar cells; Chx10; COS Cells; Cysteine Endopeptidases - metabolism; Danio rerio; Electrophoresis, Polyacrylamide Gel; Eye and associated structures. Visual pathways and centers. Vision; Eye Proteins - genetics; Eye Proteins - metabolism; Freshwater; Fundamental and applied biological sciences. Psychology; Gene Expression; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Multienzyme Complexes - metabolism; Proteasome Endopeptidase Complex; Protein Processing, Post-Translational; Rabbits; Reticulocytes - metabolism; Retina; Retina - growth & development; Transfection; Ubiquitin; Ubiquitins - metabolism; Vertebrates: nervous system and sense organs; Vsx-1 gene; Zebrafish; Zebrafish Proteins; Ubiquitin; Bipolar neuron; Transcription factor Vsx1; Retina; Eye; Visual system; Vertebrata; Brachydanio rerio; Cell line; Pisces; Development; Differentiation; Homeobox sequence
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.2000.0750048.x

: Vsx‐1 is a paired‐like : CVC homeobox protein dynamically expressed during zebrafish development. Previous results indicate that Vsx‐1 influences bipolar cell differentiation and maintenance of these cells in the adult retina. To understand the developmental regulation of this transcription factor, we investigated ubiquitination as a possible posttranslational mechanism. In vitro, Vsx‐1 was conjugated with multiple ubiquitin moieties. Proteasome inhibitors and added ubiquitin increased the accumulation of Vsx‐1‐ubiquitinn complexes and stabilized unmodified Vsx‐1. Also, in transiently transfected COS‐7 cells, Vsx‐1 is ubiquitinated, and pulse‐chase experiments show that Vsx‐1 proteolysis occurs. Vsx‐1 proteins with C‐terminal deletions retained the capacity for initial modification by ubiquitin but lost the capacity for efficient chain elongation. These results show that Vsx‐1 is a substrate of the ubiquitin/proteasome pathway and suggest that C‐terminal sequences of Vsx‐1 are critical for ubiquitin chain elongation. In addition, our findings suggest that ubiquitin‐dependent proteolysis regulates Vsx‐1 during zebrafish retinal development.