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Cheong M.S.,PMBBRC | Park H.C.,PMBBRC | Bohnert H.J.,PMBBRC | Bressan R.A.,PMBBRC | Yun D.-J.,PMBBRC
Plant Signaling and Behavior | Year: 2010

Small ubiquitin-like modifier (SUMO) is a post-translational modifier peptide that is involved in several biological processes in eukaryotes. Arabidopsis SIZ1, a SUMO E3 ligase, is an ortholog of the mammalian PIAS (Protein Inhibitor of Activated STAT) and yeast SIZ (SAP/Miz) proteins. SIZ1 contains all of the typical domains of PIAS/SIZtype proteins, such as the SAP, PINIT, SP-RING and plant-specific PHD domains. SIZ1 plays a pivotal role in controlling SUMOylation, and disruption of its function has been reported to affect stress responses, growth and development. We performed a structural and functional analysis of SIZ1 by determining the phenotypes of siz1 knockout mutants transformed with SIZ1 alleles carrying point mutations in predicted SIZ1 domains. This study establishes that the diverse properties characteristic of SIZ1 are associated with specific domains and that they can be separated. © 2010 Landes Bioscience.

Biochemical and Biophysical Research Communications | Year: 2010

Caveolin-2 regulation of insulin receptor (IR) tyrosine kinase activity was investigated. An insulin time course revealed that rapidly induced tyrosine phosphorylation of IR was steadily maintained over a 180 min time period. In parallel, insulin-exerted IR interaction with caveolin-2 was detected as early as 5 min throughout until 180 min. Down-regulation of caveolin-2 by caveolin-2 siRNA arrested specifically a long term activation of IR. The attenuation of IR activation resulted in retardation of rapamycin-sensitive pS727-STAT3 activation. As caveolin-2 tyrosine mutants were examined, Y27A-caveolin-2 explicitly impeded the long term IR activation by insulin, enhanced tyrosine dephosphorylation of IR, impaired tyrosine phosphorylation of IRS-1, and exerted the interaction between activated IR and SOCS-3. Together, we propose that pY27-caveolin-2 prolongs IR activation by its interaction with IR, thereby preventing IR interaction with SOCS-3. © 2009 Elsevier Inc. All rights reserved.

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