Alpha actinins (ACTNs) are known for their ability to modulate cytoskeletal organization and cell motility by cross-linking actin filaments. We show here that ACTN4 harbors a functional LXXLL receptor interaction motif, interacts with nuclear receptors in vitro and in mammalian cells, and potently activates transcription mediated by nuclear receptors. Whereas overexpression of ACTN4 potentiates estrogen receptor ␣ (ER␣)-mediated transcription in transient transfection reporter assays, knockdown of ACTN4 decreases it. In contrast, histone deacetylase 7 (HDAC7) inhibits estrogen receptor ␣ (ER␣)-mediated transcription. Moreover, the ACTN4 mutant lacking the CaM (calmodulin)-like domain that is required for its interaction with HDAC7 fails to activate transcription by ER␣. Chromatin immunoprecipitation (ChIP) assays demonstrate that maximal associations of ACTN4 and HDAC7 with the pS2 promoter are mutually exclusive. Knockdown of ACTN4 significantly decreases the expression of ER␣ target genes including pS2 and PR and also affects cell proliferation of MCF-7 breast cancer cells with or without hormone, whereas knockdown of HDAC7 exhibits opposite effects. Interestingly, overexpression of wild-type ACTN4, but not the mutants defective in interacting with ER␣ or HDAC7, results in an increase in pS2 and PR mRNA accumulation in a hormone-dependent manner. In summary, we have identified ACTN4 as a novel, atypical coactivator that regulates transcription networks to control cell growth.The alpha actinins (ACTNs) 2 belong to a family of cytoskeletal proteins that bind actin filaments to maintain cytoskeletal structure and cell morphology (1). Among the four members of the family, ACTN2 and ACTN3 are expressed primarily in muscle, while ACTN1 and ACTN4 are ubiquitously expressed (2). All four members of the actinin family share high sequence homology with conserved functional domains including an N-terminal actin-binding domain containing two highly conserved calponin homology (CH1 and CH2) domains, a central domain consisting of four spectrin repeats (SR), two EF hand calcium-binding domains and a C-terminal calmodulin (CaM)-like domain (3). Although predominantly localized in the cytoskeleton, ACTN4 is also found in the nucleus of certain cell types and is capable of translocating to the nucleus in response to extracellular stimuli (4). In addition to its role in the cytosol, we have recently identified a novel function for ACTN4 in transcriptional regulation by myocyte enhancer factor 2 (MEF2) (5). Another study has also demonstrated an association between ACTN4 and nuclear factor B (NF-B) (6). These findings suggest that ACTN4 may play an unexpected role in transcriptional regulation.Nuclear hormone receptors, including vitamin D receptor (VDR) and steroid hormone receptors such as estrogen receptors (ER) are ligand-activated transcription factors that control aspects of homeostasis, cell differentiation, proliferation, and development (7-9). Transcriptional regulation by nuclear receptors is thought to occur through t...

Promyelocytic leukemia protein (PML) sumoylation has been proposed to control the formation of PML nuclear bodies (NBs) and is crucial for PML-dependent cellular processes, including apoptosis and transcriptional regulation. However, the regulatory mechanisms of PML sumoylation and its specific roles in the formation of PML NBs remain largely unknown. Here, we show that histone deacetylase 7 (HDAC7) knockdown reduces the size and the number of the PML NBs in human umbilical vein endothelial cells (HUVECs). HDAC7 coexpression stimulates PML sumoylation independent of its HDAC activity. Furthermore, HDAC7 associates with the E2 SUMO ligase, Ubc9, and stimulates PML sumoylation in vitro, suggesting that it possesses a SUMO E3 ligase-like activity to promote PML sumoylation. Importantly, HDAC7 knockdown inhibits tumor necrosis factor alpha-induced PML sumoylation and the formation of PML NBs in HUVECs. These results demonstrate a novel function of HDAC7 and provide a regulatory mechanism of PML sumoylation.

The tumor suppressor promyelocytic leukemia protein (PML) predominantly resides in a structurally distinct sub-nuclear domain called PML nuclear bodies. Emerging evidences indicated that PML actively participates in many aspects of cellular processes, but the molecular mechanisms underlying PML regulation in response to stress and environmental cues are not complete. Post-translational modifications, such as SUMOylation, phosphorylation, acetylation, and ubiquitination of PML add a complex layer of regulation to the physiological function of PML. In this review, we discuss the fast-moving horizon of post-translational modifications targeting PML.

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In a secure data sharing system, users can selectively retrieve encrypted files by performing keyword search over the ciphertext of data. Most of the existing searchable encryption schemes can provide security protection for both data owner and users. Nevertheless, three pivotal issues need to be addressed. Firstly, the cloud might return a wrong result or incomplete result for some reasons, e.g., saving the computing resources. Secondly, users need to store massive keys to generate trapdoors and decrypt the ciphertext of data, which brings great challenges to users' key management. Thirdly, when users perform keyword search over a large number of files, they need to generate and submit massive trapdoors, which is unrealistic. Proceeding from these points, in this paper, we propose an efficient verifiable key-aggregate keyword searchable encryption (EVKAKSE) scheme. In this scheme, the data owner distributes only one aggregate key to users for keyword search, decryption and verification, who can use the aggregate key to generate a single trapdoor for keyword search over shared files. Generally, we define the requirements of the scheme, analyze the threat models and give a valid construction. Furthermore, our security analysis and experimental evaluation demonstrate that the scheme is efficient and secure.

Background: PML is highly expressed in endothelial cells (ECs), but its role in ECs remains largely unexplored. Results: PML is critical for TNF␣-and IFN␣-mediated inhibition of EC network formation and migration. Conclusion: PML is an angiogenesis inhibitor following inflammation-associated cytokine signaling. Significance: PML is a novel regulator of endothelial cell physiology.

We have identified G protein suppressor 2 (GPS2) as a stable component of the SMRT corepressor complexes. GPS2 potently represses basal transcription, with the repression domain mapped to the N-terminal silencing mediator of retinoic acid and thyroid hormone receptor (SMRT)-interacting domain. Knockdown of GPS2 abrogates, whereas overexpression potentiates, SMRT-mediated repression activity. The SMRT complexes are involved in 4-hydroxyl-tamoxifen (4OHT)-mediated gene repression by estrogen receptor ␣ (ER␣). We show that 4OHT recruits SMRT and GPS2 to the promoter of pS2, an ER␣ target gene, in a dynamic manner. Unexpectedly, we also found that estradiol (E2) promotes promoter recruitment of the SMRT complexes. While knockdown of GPS2 compromised 4OHT-mediated repression, it enhanced E2-induced expression of a reporter gene and several endogenous ER␣ target genes, including pS2, cyclin D1 (CCND1), progesterone receptor (PR), and c-MYC. Finally, we show that depletion of GPS2 or SMRT by siRNA promotes cell proliferation in MCF-7 breast cancer cells. Thus, we concluded that GPS2 is an integral component of the SMRT complexes, important for ligand-dependent gene regulations by ER␣ and a suppressor for MCF-7 cell proliferation. Transcriptional regulation by estrogen receptor ␣ (ER␣)2 is mediated by transcriptional coactivators and corepressors. SMRT and N-CoR are two closely related transcriptional corepressors that mediate transcriptional repression by many nuclear hormone receptors including ER␣ (1-5). Both SMRT and N-CoR are large nuclear proteins that contain multiple functional domains, including four repression domains (RDs) (2, 4, 6, 7). Transcriptional repression by SMRT or N-CoR is manifested through their recruitment of a histone deacetylase (HDAC) complex containing mSin3A and HDAC1 (6 -8). In addition, SMRT and N-CoR also interact with HDAC3 (9 -11) and with class II HDACs including HDAC4, -5, and -7 (12, 13). TBL1 and TBRL1 are also common stable components of the SMRT and N-CoR complexes (9,14). Despite this long list, SMRT and N-CoR are large proteins, and other components of their complexes undoubtedly exist but have not yet been identified.GPS2 (G protein suppressor 2) was first identified as a suppressor of G protein-activated MAPK signaling in both yeast and mammalian cells (16,17). GPS2 is also involved in transcription regulation through its association with the papillomavirus E2 and E6 proteins (18,19), the human T-cell lymphotrophic viral oncoprotein Tax (20), p53 and p300 (18,19,21), and regulatory factor X4 variant transcript 3 (RFX4_v3) (22). GPS2 was also found in the N-CoR corepressor complex and is capable of repressing basal transcription when forcibly bound to a promoter (23). Besides transcription regulation, previous studies suggested that GPS2 is involved in cell cycle regulation, DNA repair, cytoskeleton architecture, brain development, and metabolism (22, 24 -29). These data indicate that GPS2 is involved in multiple cellular pathways.To better understand the mechanisms by which SM...

Promyelocytic leukemia protein (PML) nuclear bodies (NBs) are dynamic subnuclear compartments that play roles in several cellular processes, including apoptosis, transcriptional regulation, and DNA repair. Histone deacetylase (HDAC) 7 is a potent corepressor that inhibits transcription by myocyte enhancer factor 2 (MEF2) transcription factors. We show here that endogenous HDAC7 and PML interact and partially colocalize in PML NBs. Tumor necrosis factor (TNF)-alpha treatment recruits HDAC7 to PML NBs and enhances association of HDAC7 with PML in human umbilical vein endothelial cells. Consequently, TNF-alpha promotes dissociation of HDAC7 from MEF2 transcription factors and the promoters of MEF2 target genes such as matrix metalloproteinase (MMP)-10, leading to accumulation of MMP-10 mRNA. Conversely, knockdown of PML enhances the association between HDAC7 and MEF2 and decreases MMP-10 mRNA accumulation. Accordingly, ectopic expression of PML recruits HDAC7 to PML NBs and leads to activation of MEF2 reporter activity. Notably, small interfering RNA knockdown of PML decreases basal and TNF-alpha-induced MMP-10 mRNA accumulation. Our results reveal a novel mechanism by which PML sequesters HDAC7 to relieve repression and up-regulate gene expression.