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 beta-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

p53 plays a pivotal role in tumour suppression under stresses, such as DNA damage. ISG15 has been implicated in the control of tumorigenesis. Intriguingly, the expression of ISG15, UBE1L and UBCH8 is induced by DNA-damaging agents, such as ultraviolet and doxorubicin, which are known to induce p53. Here, we show that the genes encoding ISG15, UBE1L, UBCH8 and EFP, have the p53-responsive elements and their expression is induced in a p53-dependent fashion under DNA damage conditions. Furthermore,

Many inhibitor of apoptosis (IAP) family proteins inhibit apoptosis. IAPs contain N-terminal baculovirus IAP repeat domains and a C-terminal RING ubiquitin ligase domain. Drosophila IAP DIAP1 is essential for the survival of many cells, protecting them from apoptosis by inhibiting active caspases. Apoptosis initiates when proteins such as Reaper, Hid, and Grim bind a surface groove in DIAP1 baculovirus IAP repeat domains via an N-terminal IAP-binding motif. This evolutionarily conserved interact

HslVU is an ATP-dependent protease consisting of HslU ATPase and HslV peptidase. In an HslVU complex, the central pores of HslU hexamer and HslV dodecamer are aligned and the proteolytic active sites are sequestered in the inner chamber of HslV. Thus, the degradation of natively folded proteins requires unfolding and translocation processes for their access into the proteolytic chamber of HslV. A highly conserved GYVG(93) sequence constitutes the central pore of HslU ATPase. To determine the rol

Identification of the cellular mechanisms that mediate cancer cell chemosensitivity is important for developing new cancer treatment strategies. Several chemotherapeutic drugs increase levels of the posttranslational modifier ISG15, which suggests that ISGylation could suppress oncogenesis. However, how ISGylation of specific target proteins controls tumorigenesis is unknown. Here, we identified proteins that are ISGylated in response to chemotherapy. Treatment of a human mammary epithelial cell