Jae-hong Seol

Daxx is a multifunctional protein that regulates a variety of cellular processes, including transcription, cell cycle, and apoptosis. SPOP is a BTB (Bric-a-brac/Tramtrack/Broad complex) protein that constitutes Cul3-based ubiquitin ligases. Here we show that SPOP serves as an adaptor of Daxx for the ubiquitination by Cul3-based ubiquitin ligase and subsequent degradation by the proteasome. Expression of SPOP with Cul3 markedly reduced Daxx level, and this degradation was blocked by SPOP-specific

Ubiquitin-fold modifier 1 (Ufm1) is a recently identified new ubiquitin-like protein, whose tertiary structure displays a striking resemblance to ubiquitin. Similar to ubiquitin, it has a Gly residue conserved across species at the C-terminal region with extensions of various amino acid sequences that need to be processed in vivo prior to conjugation to target proteins. Here we report the isolation, cloning, and characterization of two novel mouse Ufm1-specific proteases, named UfSP1 and UfSP2.

Skp1p-cullin-F-box protein (SCF) complexes are ubiquitin-ligases composed of a core complex including Skp1p, Cdc53p, Hrt1p, the E2 enzyme Cdc34p, and one of multiple F-box proteins which are thought to provide substrate specificity to the complex. Here we show that the F-box protein Rcy1p is required for recycling of the v-SNARE Snc1p in Saccharomyces cerevisiae. Rcy1p localized to areas of polarized growth, and this polarized localization required its CAAX box and an intact actin cytoskeleton.

FLOWERING LOCUS T (FT) plays a key role as a mobile floral induction signal that initiates the floral transition. Therefore, precise control of FT expression is critical for the reproductive success of flowering plants. Coexistence of bivalent histone H3 lysine 27 trimethylation (H3K27me3) and H3K4me3 marks at the FT locus and the role of H3K27me3 as a strong FT repression mechanism in Arabidopsis have been reported. However, the role of an active mark, H3K4me3, in FT regulation has not been add

A combined multidimensional chromatography-mass spectrometry approach known as "MudPIT" enables rapid identification of proteins that interact with a tagged bait while bypassing some of the problems associated with analysis of polypeptides excised from SDS-polyacrylamide gels. However, the reproducibility, success rate, and applicability of MudPIT to the rapid characterization of dozens of proteins have not been reported. We show here that MudPIT reproducibly identified bona fide partners for bu

The hslVU operon in Escherichia coli encodes two heat shock proteins, HslV, a 19-kDa protein homologous to β-type subunits of the 20 S proteasomes, and HslU, a 50-kDa protein related to the ATPase ClpX. We have recently shown that HslV and HslU can function together as a novel ATP-dependent protease, the HslVU protease. We have now purified both proteins to apparent homogeneity from extracts of E. coli carrying the hslVU operon on a multicopy plasmid. HslU by itself cleaved ATP, and pure HslV is

The Hippo pathway plays crucial roles in regulating organ size and stem cell homeostasis. Although the signalling cascade of the core Hippo kinases is relatively well understood, little is known about the mechanisms that modulate the activity of the Hippo pathway. Here, we report identification of NEDD4, a HECT-type E3 ubiquitin ligase, as a regulatory component of the Hippo pathway. We demonstrate that NEDD4 ubiquitylates and destabilizes WW45 and LATS kinase, both of which are required for act

HslVU in Escherichia coli a new two-component ATP-dependent protease composed of two heat-shock proteins, the HslU ATPase and the HslV peptidase which is related to proteasome beta-type subunits. Here we show that the reconstituted HslVU enzyme degrades not only certain hydrophobic peptides but also various polypeptides, including insulin B-chain, casein, and carboxymethylated lactalbumin. Maximal proteolytic activity was obtained with a 1:2 molar ratio of HslV (a 250-kDa complex) to HslU (a 450

The generation of reactive oxygen species (ROS) is required for proper cell signaling, but must be tightly regulated to minimize deleterious oxidizing effects. Activation of the NADPH oxidases (Nox) triggers ROS production and, thus, regulatory mechanisms exist to properly control Nox activity. In this study, we report a novel mechanism in which Nox1 activity is regulated through the proteasomal degradation of Nox organizer 1 (NoxO1). We found that through the interaction between NoxO1 and growt

ClpA is the ATPase component of the ATP-dependent protease Ti (Clp) in Escherichia coli and contains two ATP-binding sites. A ClpA variant (referred to as ClpAT) carrying threonine in place of the 169th methionine has recently been shown to be highly soluble but indistinguishable from the wild-type, 84-kDa ClpA in its ability to hydrolyze ATP and to support the casein-degrading activity of ClpP. Therefore, site-directed mutagenesis was performed to generate mutations in either of the two ATP-bin