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Transient, multi-protein complexes are important facilitators of cellular functions. This includes the chaperome, an abundant protein family comprising chaperones, co-chaperones, adaptors, and folding enzymes--dynamic complexes of which regulate cellular homeostasis together with the protein degradation machinery1-6. Numerous studies have addressed the role of chaperome members in isolation, yet little is known about their relationships regarding how they interact and function together in malignancy7-17. As function is probably highly dependent on endogenous conditions found in native tumours, chaperomes have resisted investigation, mainly due to the limitations of methods needed to disrupt or engineer the cellular environment to facilitate analysis. Such limitations have led to a bottleneck in our understanding of chaperome-related disease biology and in the development of chaperome-targeted cancer treatment. Here we examined the chaperome complexes in a large set of tumour specimens. The methods used maintained the endogenous native state of tumours and we exploited this to investigate the molecular characteristics and composition of the chaperome in cancer, the molecular factors that drive chaperome networks to crosstalk in tumours, the distinguishing factors of the chaperome in tumours sensitive to pharmacologic inhibition, and the characteristics of tumours that may benefit from chaperome therapy. We find that under conditions of stress, such as malignant transformation fuelled by MYC, the chaperome becomes biochemically 'rewired' to form a network of stable, survivalfacilitating, high-molecular-weight complexes. The chaperones heat shock protein 90 (HSP90) and heat shock cognate protein 70 (HSC70) are nucleating sites for these physically and functionally integrated complexes. The results indicate that these tightly integrated chaperome units, here termed the epichaperome, can function as a network to enhance cellular survival, irrespective of tissue of origin or genetic background. The epichaperome, present in over half of all cancers tested, has implications for diagnostics and also provides potential vulnerability as a target for drug intervention. [ABSTRACT FROM AUTHOR]

Estrogen receptor α (ERα) is a ligand-dependent transcription factor that mediates physiological responses to 17β-estradiol (E2). These responses of cells to estrogen are regulated in part by degradation of ERα. In this report, we found that CDK11p58 repressed ERα transcriptional activity. And we further demonstrated that ERα protein level was down-regulated by CDK11p58 in mammalian cells in a ligand independent manner. This effect could be abrogated by treatment with proteasome inhibitor MG132. Our results indicated that the ubiquitin/proteasome-mediated degradation of ERα was promoted by CDK11p58. Furthermore, the interaction between ERα and CDK11p58 was detected. This interaction was necessary for the polyubiquitination and degradation of ERα. On the contrary, the other isoform of CDK11, CDK11p110 and the kinase dead mutant of CDK11p58, D224N, did not associate with ERα and failed to reduce the ERα protein level. These data identified a new negative regulatory protein of ERα and provided a new pathway by which CDK11p58 negatively regulated cells. [ABSTRACT FROM PUBLISHER]

Abstract  CDK11p58, a G2/M-specific protein kinase, has been shown to be associated with apoptosis in many cell lines, with largely unknown mechanisms. Our previous study proved that CDK11p58-enhanced cycloheximide (CHX)-induced apoptosis in SMMC-7721 hepatocarcinoma cells. Here we report for the first time that ectopic expression of CDK11p58 down-regulates Bcl-2 expression and its Ser70, Ser87 phosphorylation in CHX-induced apoptosis in SMMC-7721 cells. Overexpression of Bcl-2 counteracts the pro-apoptotic activity of CDK11p58. Furthermore, we confirm that the kinase activity of CDK11p58 is essential to the down-regulation of Bcl-2 as well as apoptosis. Taken together, these results demonstrate that CDK11p58 down-regulates Bcl-2 in pro-apoptosis pathway depending on its kinase activity, which elicits survival signal in hepatocarcinoma cells. [ABSTRACT FROM AUTHOR]

Abstract  Our previous studies have shown that overexpression of ?1,4-galactosyltransferase1 (?1,4GT1) leads to increased apoptosis induced by cycloheximide (CHX) in SMMC-7721 human hepatocarcinoma cells. However, the role of ?1,4GT1 in apoptosis remains unclear. Here we demonstrated that cell surface ?1,4GT1 inhibited the autophosphorylation of epidermal growth factor receptor (EGFR) especially at Try 1068. The phosphorylation of protein kinase B (PKB/Akt) and extracellular signal-regulated protein kinase1/2 (ERK1/2), which are downstream molecules of EGFR, were also reduced in cell surface ?1,4GT1-overexpressing cells. Furthermore, the translocations of Bad and Bax that are regulated by PKB/Akt and ERK1/2 were also increased in these cells. As a result, the release of cytochrome c from mitochondria to cytosol was increased and caspase-3 was activated. In contrast, RNAi-mediated knockdown of ?1,4GT1 increased the autophosphorylation of EGFR. These results demonstrated that cell surface ?1,4GT1 may negatively regulate cell survival possibly through inhibiting and modulating EGFR signaling pathway. [ABSTRACT FROM AUTHOR]

Abstract Protein kinases are important signalling molecules critical for normal cell growth and development. CDK11p58 is a p34cdc2-related protein kinase, and plays an important role in normal cell cycle progression. In this study, we mainly characterized the protein expression of CDK11p58 during postnatal development in mouse testes and examined the cellular localization of CDK11p58 and cyclinD3, which was associated with CDK11p58 in mammalian cells. Western blot analysis revealed that CDK11p58 was present in the early stages of development. It gradually increased and reached a peak in adult testes. The protein expression of CDK11p58 was further analysed by immunohistochemistry due to its developmentally regulated expression. The variable immunostaining patterns of CDK11p58 were visualized during different developmental periods and, in adult mouse, different stages of seminiferous tubules. CDK11p58 expression was detected in proliferating germ cells in the early stages of developing testes. In adult testes, the protein was expressed in pachytene primary spermatocytes from stage VII to XI of spermatogenesis and in postmeiotic spermatids in all stages at different levels. The colocalization of CDK11p58 and cyclinD3 in the adult testeis was revealed by immunofluorescence analysis. (Mol Cell Biochem 270: 99–106, 2005) [ABSTRACT FROM AUTHOR]

Transcription factor E1AF is widely known to play critical roles in tumor metastasis via directly binding to the promoters of genes involved in tumor migration and invasion. Here, we report for the first time E1AF as a novel binding partner for ubiquitously expressed Sp1 transcription factor. E1AF forms a complex with Sp1, contributes to Sp1 phosphorylation and transcriptional activity, and functions as a mediator between epidermal growth factor and Sp1 phosphorylation and activity. Sp1 functions as a carrier bringing E1AF to the promoter region, thus activating transcription of glioma-related gene for ß1,4-galactosyltransferase V (GalT V; EC 2.4.1.38). Biologically, E1AF functions as a positive invasion regulator in glioma in cooperation with Sp1 partly via up-regulation of GalT V. This report describes a new mechanism of glioma invasion involving a cooperative effort between E1AF and Sp1 transcription factors. [ABSTRACT FROM AUTHOR]

Androgen receptor (AR) is essential for the maintenance of the male reproductive systems and is critical for the carcinogenesis of human prostate cancers (PCas). D-type cyclins are closely related to the repression of AR function. It has been well documented that cyclin D1 inhibits AR function through multiple mechanisms, but the mechanism of how cyclin D3 exerts its repressive role in the AR signaling pathway remains to be identified. In the present investigation, we demonstrate that cyclin D3 and the 58-kDa isoform of cyclin-dependent kinase 11 (CDK11p58) repressed AR transcriptional activity as measured by reporter assays of transformed cells and prostate-specific antigen expression in PCa cells. AR, cyclin D3, and CDK11p58 formed a ternary complex in cells and were colocalized in the luminal epithelial layer of the prostate. AR activity is controlled by phosphorylation at specific sites. We found that AR was phosphorylated at Ser-308 by cyclin D3/CDK11p58 in vitro and in vivo, leading to the repressed activity of AR transcriptional activation unit 1 (TAU1). Furthermore, androgen-dependent proliferation of PCa cells was inhibited by cyclin D3/CDK11p58 through AR repression. These data suggest that cyclin D3/CDK11p58 signaling is involved in the negative regulation of AR function. [ABSTRACT FROM AUTHOR]