Novel biphasic mechanism of the canonical Wnt signalling component PYGO2 promotes cardiomyocyte differentiation from hUC-MSCs.

Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) are used to regenerate the myocardium during cardiac repair after myocardial infarction. However, the regulatory mechanism underlying their ability to form mesodermal cells and differentiate into cardiomyocytes remains unclear. Here, we established a human-derived MSCs line isolated from healthy umbilical cords and established a cell model of the natural state to examine the differentiation of hUC-MSCs into cardiomyocytes. Quantitative RT-PCR, western blotting, immunofluorescence, flow cytometry, RNA Seq, and inhibitors of canonical Wnt signalling were used to detect the germ-layer markers T and MIXL1; the markers of cardiac progenitor cells MESP1, GATA4, and NKX2.5 and the cardiomyocyte-marker cTnT to identify the molecular mechanism associated with PYGO2, a key component of the canonical Wnt signalling pathway that regulates the formation of cardiomyocyte-like cells. We demonstrated that PYGO2 promotes the formation of mesodermal-like cells and their differentiation into cardiomyocytes through the hUC-MSC-dependent canonical Wnt signalling by promoting the early-stage entry of ß-catenin into the nucleus. Surprisingly, PYGO2 did not alter the expression of the canonical-Wnt, NOTCH, or BMP signalling pathways during the middle-late stages. In contrast, PI3K-Akt signalling promoted hUC-MSCs formation and their differentiation into cardiomyocyte-like cells. To the best of our knowledge, this is the first study to demonstrate that PYGO2 uses a biphasic mechanism to promote cardiomyocyte formation from hUC-MSCs.

miR-590-5p targets RMND5A and promotes migration in pancreatic adenocarcinoma cell lines.

Required for meiotic nuclear division 5 homolog A (RMND5A) functions as an E3 ubiquitin ligase. To date, few studies have investigated the role of RMND5A in cancer. In the present study, the expression levels of RMND5A in multiple types of cancer were analyzed using the Gene Expression Profiling Interactive Analysis platform. The results revealed that RMND5A was highly expressed and associated with overall survival in patients with pancreatic adenocarcinoma (PAAD). A wound-healing assay revealed that RMND5A overexpression significantly increased cell migration in the PAAD cell lines AsPC-1 and PANC-1. In silico analysis predicted that RMND5A was a potential target of microRNA(miR)-590-5p. Further in vitro experiments demonstrated that overexpression of miR-590-5p downregulated the expression levels of RMND5A and decreased the migratory ability of the AsPC-1 and PANC-1 cell lines. In addition, overexpression of miR-590-5p attenuated the promoting effects of RMND5A on the migration of AsPC-1 and PANC-1 cells. The results of the present study may further elucidate the mechanisms underlying PAAD progression and provide novel targets for the treatment of PAAD.

Pygo1 regulates pathological cardiac hypertrophy via a ß-catenin-dependent mechanism.

Wnt/ß-catenin signaling plays a key role in pathological cardiac remodeling in adults. The identification of a tissue-specific Wnt/ß-catenin interaction factor may provide a tissue-specific clinical targeting strategy. Drosophila Pygo encodes the core interaction factor of Wnt/ß-catenin. Two Pygo homologs (Pygo1 and Pygo2) have been identified in mammals. Different from the ubiquitous expression profile of Pygo2, Pygo1 is enriched in cardiac tissue. However, the role of Pygo1 in mammalian cardiac disease is yet to be elucidated. In this study, we found that Pygo1 was upregulated in human cardiac tissues with pathological hypertrophy. Cardiac-specific overexpression of Pygo1 in mice spontaneously led to cardiac hypertrophy accompanied by declined cardiac function, increased heart weight/body weight and heart weight/tibial length ratios, and increased cell size. The canonical ß-catenin/T-cell transcription factor 4 (TCF4) complex was abundant in Pygo1-overexpressing transgenic (Pygo1-TG) cardiac tissue, and the downstream genes of Wnt signaling, that is, Axin2, Ephb3, and c-Myc, were upregulated. A tail vein injection of ß-catenin inhibitor effectively rescued the phenotype of cardiac failure and pathological myocardial remodeling in Pygo1-TG mice. Furthermore, in vivo downregulated pygo1 during cardiac hypertrophic condition antagonized agonist-induced cardiac hypertrophy. Therefore, our study is the first to present in vivo evidence demonstrating that Pygo1 regulates pathological cardiac hypertrophy in a canonical Wnt/ß-catenin-dependent manner, which may provide new clues for tissue-specific clinical treatment via targeting this pathway.NEW & NOTEWORTHY In this study, we found that Pygo1 is associated with human pathological hypertrophy. Cardiac-specific overexpression of Pygo1 in mice spontaneously led to cardiac hypertrophy. Meanwhile, cardiac function was improved when expression of Pygo1 was interfered in hypertrophy-model mice. Our study is the first to present in vivo evidence demonstrating that Pygo1 regulates pathological cardiac hypertrophy in a canonical Wnt/ß-catenin-dependent manner, which may provide new clues for a tissue-specific clinical treatment targeting this pathway.

BVES downregulation in non-syndromic tetralogy of fallot is associated with ventricular outflow tract stenosis.

BVES is a transmembrane protein, our previous work demonstrated that single nucleotide mutations of BVES in tetralogy of fallot (TOF) patients cause a downregulation of BVES transcription. However, the relationship between BVES and the pathogenesis of TOF has not been determined. Here we reported our research results about the relationship between BVES and the right ventricular outflow tract (RVOT) stenosis. BVES expression was significantly downregulated in most TOF samples compared with controls. The expression of the second heart field (SHF) regulatory network genes, including NKX2.5, GATA4 and HAND2, was also decreased in the TOF samples. In zebrafish, bves knockdown resulted in looping defects and ventricular outflow tract (VOT) stenosis, which was mostly rescued by injecting bves mRNA. bves knockdown in zebrafish also decreased the expression of SHF genes, such as nkx2.5, gata4 and hand2, consistent with the TOF samples` results. The dual-fluorescence reporter system analysis showed that BVES positively regulated the transcriptional activity of GATA4, NKX2.5 and HAND2 promoters. In zebrafish, nkx2.5 mRNA partially rescued VOT stenosis caused by bves knockdown. These results indicate that BVES downregulation may be associated with RVOT stenosis of non-syndromic TOF, and bves is probably involved in the development of VOT in zebrafish.

FKBP51 induces p53-dependent apoptosis and enhances drug sensitivity of human non-small-cell lung cancer cells.

Lung cancer is one of the most prevalent cancer types worldwide, and non-small-cell lung cancer (NSCLC) accounts for ~85% of all lung cancer cases. Despite the notable prevalence of NSCLC, the mechanisms underlying its progression remain unclear. The present study investigated the involvement of FK506-binding protein 51 (FKBP51) in NSCLC development and determined the factors associated with FKBP51 modification for NSCLC treatment. Immunohistochemical analysis was performed to analyze FKBP51 expression in human NSCLC tissue samples. Additionally, flow cytometry was performed to observe the apoptosis of FKBP51-overexpressing A549 cells. A dual-luciferase reporter assay was performed to confirm the association between FKBP51 and p53 expression, and western blotting was performed to analyze the effects of FKBP51 on the p53 signaling pathway. Finally, cell viability was measured using a Cell Counting Kit-8 assay. The results suggested FKBP51 downregulation in human lung cancer. Furthermore, apoptosis rates may be increased in FKBP51-overexpressing A549 cells. Moreover, FKBP51 promoted p53 expression and subsequent p53 signaling pathway activation. These results indicated that FKBP51 promoted A549 cell apoptosis via the p53 signaling pathway. Additionally, FKBP51 enhanced the sensitivity of A549 cells to cisplatin. Collectively, these data suggested that FKBP51 could serve as a biomarker for human lung cancer and can thus be tailored for incorporation into NSCLC therapy in the future.

TRIM45 Suppresses the Development of Non-small Cell Lung Cancer.

BACKGROUND: Previously, we first identified the human tripartite motifcontaining protein 45 (TRIM45) acts as a novel transcriptional repressor in mitogenactivated protein kinase (MAPK) signaling pathway. After that, the inhibitory role of TRIM45 in the development of tumor was gradually unveiled. However, the function of TRIM45 in the tumorigenesis of lung cancer has not been characterized. METHODS AND RESULTS: In this study, we found that TRIM45 was up-regulated in earlystage human non-small-cell lung cancer (NSCLC) tissues. Overexpression of TRIM45 in lung cancer cells induces G1 arrest and promotes apoptosis, which accompanied by upregulated expression of RB, p16, p53, p27Kip1, and Caspase3 and down-regulated expression of CyclinE1 and CyclinE2. Further detection of the expression of the molecules in the MAPK signaling pathway revealed that overexpression of TRIM45 in lung cancer cells promotes phosphorylated p38 (p-p38) activation and inhibits phosphorylated ERK (p-ERK) activation. In accordance with this, p-p38 is increased while p-ERK is decreased in lung cancer tissues. CONCLUSION: These findings indicate that TRIM45 plays an inhibitory role in the tumorigenesis of lung cancer. High-level expression of TRIM45 in lung cancer tissue may promote cell apoptosis by activating p38 signal and inhibit proliferation by down-regulating p-ERK, which provides a new clue for understanding the tumorigenesis of lung cancer.

The Functional Polymorphism R129W in the BVES Gene Is Associated with Sporadic Tetralogy of Fallot in the Han Chinese Population.

Background: Tetralogy of Fallot (TOF) accounts for ∼10% of congenital heart disease cases. The blood vessel epicardial substance (BVES) gene has been reported to play a role in the function of adult hearts. However, whether allelic variants in BVES contribute to the risk of TOF and its possible mechanism remains unknown. Methods: The open reading frame of the BVES gene was sequenced using samples from 146 TOF patients and 100 unrelated healthy controls. qRT-PCR and western blot assays were used to confirm the expression of mutated BVES variants in the TOF samples. The online software Polyphen2 and SIFT were used to predict the deleterious effects of the observed allelic variants. The effects of these allelic variants on the transcriptional activities of genes were examined using dual-fluorescence reporter assays. Results: We genotyped four single nucleotide polymorphisms (SNPs) in the BVES gene from each of the 146 TOF patients. Among them, the minor allelic frequencies of c.385C>T (p.R129W) were 0.035% in TOF, but ∼0.025% in 100 controls and the Chinese Millionome Database. This allelic variant was predicted to be a potentially harmful alteration by the Polyphen2 and SIFT softwares. qRT-PCR and western blot analyses indicated that the expression of BVES in the six right ventricular outflow tract samples with the c.385C>T allelic variant was significantly downregulated. A dual-fluorescence reporter system showed that the c.385C>T allelic variant significantly decreased the transcriptional activity of the BVES gene and also decreased transcription from the GATA4 and NKX2.5 promoters. Conclusions: c.385C>T (p.R129W) is a functional SNP of the BVES gene that reduces the transcriptional activity of BVES in vitro and in vivo in TOF tissues. This subsequently affects the transcriptional activities of GATA4 and NKX2.5 related to TOF. These findings suggest that c.385C>T may be associated with the risk of TOF in the Han Chinese population.

Loss of the Nodal modulator Nomo results in chondrodysplasia in zebrafish.

BACKGROUND: Transforming growth factor-ß (TGF-ß)/nodal signaling is involved in early embryonic patterning in vertebrates. Nodal modulator (Nomo, also called pM5) is a negative regulator of nodal signaling. Currently, the role of nomo gene in cartilage development in vertebrates remains unknown. METHODS: Nomo mutants were generated in a knockout model of zebrafish by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9) targeting of the fibronectin type III domain. The expression of related genes, which are critical for chondrogenesis, was analyzed by whole-mount in situ hybridization and qRT-PCR. Whole-mount alcian staining was performed to analyze the cartilage structure. RESULTS: nomo is highly expressed in various tissues including the cartilage. We successfully constructed a zebrafish nomo knockout model. nomo homozygous mutants exhibited varying degrees of hypoplasia and dysmorphism on 4 and 5 dpf, which is similar to chondrodysplasia in humans. The key genes of cartilage and skeletal development, including sox9a, sox9b, dlx1a, dlx2a, osx, col10a1, and col11a2 were all downregulated in nomo mutants compared with the wildtype. CONCLUSION: The nomo gene positively regulates the expression of the master regulator and other key development genes involved in bone formation and cartilage development and it is essential for cartilage development in zebrafish.

CXXC5 is required for cardiac looping relating to TGFß signaling pathway in zebrafish.

BACKGROUND: CXXC-type zinc-finger protein CXXC5 has been reported to be associated with the development of cardiovascular disease. Recently, through signaling pathway screening we found that CXXC5 activated Tgfß and myocardial differentiation signaling pathways simultaneously. Although the physiological and pathological function of CXXC5 in many organs has been well elucidated, its function in heart remains unclear. METHODS AND RESULTS: Here, we found that zebrafish CXXC5 and SMAD were interacting through ZF-CXXC and MH1 domain. Over-expression of CXXC5 in cardiomyocyte increased the luciferase report activity of Tgfß signaling pathway. Spatiotemporal expression profile of cxxc5 showed that it consistently expressed during cardiogenesis. Knockdown of cxxc5 in zebrafish displayed looping defects, cardiac dysplasia, pericardial edema, and decreased contraction ability, accompanied with down-regulation of members referring to cardiac looping downstream genes of Tgfß signaling pathway, such as nkx2.5, hand2, and has2. Co-injection of hand2 mRNA with cxxc5 morpholino rescued the cardiac looping detects. CONCLUSION: Our study is the first to provide an in vivo evidence for cxxc5 regulating heart development and cardiac looping via Tgfß related signaling pathway. This finding suggested that CXXC5 may serve as a possible marker that has potential diagnostic and prognostic value in fetus with congenital heart disease.

SMYD1, an SRF-Interacting Partner, Is Involved in Angiogenesis.

Previous studies have demonstrated that Smyd1 plays a critical role in cardiomyocyte differentiation, cardiac morphogenesis and myofibril organization. In this study, we uncovered a novel function of Smyd1 in the regulation of endothelial cells (ECs). Our data showed that Smyd1 is expressed in vascular endothelial cells, and knockdown of SMYD1 in endothelial cells impairs EC migration and tube formation. Furthermore, Co-IP and GST pull-down assays demonstrated that SMYD1 is associated with the Serum Response Factor (SRF). EMSA assays further showed that SMYD1 forms a complex with SRF and enhances SRF DNA binding activity. Our studies indicate that SMYD1 serves as an SRF-interacting protein, enhances SRF DNA binding activity, and is required for EC migration and tube formation to regulate angiogenesis.

CXXC5 regulates differentiation of C2C12 myoblasts into myocytes.

CXXC5 is a member of the CXXC-type zinc-finger domain containing protein family, which is suggested to function in gene transcription, cell adhesion and cytoskeleton organization. Previous studies have revealed that CXXC5 is expressed in skeletal muscle, but whether it regulates skeletal myogenesis is yet unknown. Here, we screened for the possible signaling pathways in which CXXC5 might participate using luciferase gene reporters. The results indicated that CXXC5 significantly increased the activities of the promoters of genes involved in skeletal muscle differentiation. We therefore studied the role of CXXC5 during skeletal myogenesis in C2C12 myoblasts. Our findings suggest that overexpression of CXXC5 in C2C12 myoblasts facilitated myocyte differentiation, while RNAi interference of CXXC5 significantly inhibited the differentiation of C2C12 myoblasts. This study suggests that CXXC5 plays a significant role in regulating skeletal myogenesis.

Expression and identification of a novel gene Spata34 in mouse spermatogenic cells.

Leucine-rich repeat (LRR) containing proteins play an essential role in signal transduction, cell adhesion, cell development, DNA repair and RNA processing. Here we cloned a novel gene, Spata34, encoding a LRR containing protein of 415 aa. Spata34 gene consisted of 9 exons and 8 introns and mapped to chromosome 3qA3. Spata34 is conserved across species in evolution. The Spata34 gene was expressed at various levels, faintly before first weeks postpartum and strongly from 2 weeks postpartum in adult testes. Western blot analysis showed that Spata34 protein was specially expressed in mouse testis. Immunohistochemical analysis revealed that Spata34 protein was most abundant in the cytoplasm of round spermatids and elongating spermatids within seminiferous tubules of the adult testis. Overexpression of Spata34 in COS7 cells inhibited the transcriptional activity of AP-1, p53 and p21 which suggested that Spata34 protein may act as a transcriptional repressor in p53 and p21 pathway.

The influence of Angiotensin converting enzyme and angiotensinogen gene polymorphisms on hypertrophic cardiomyopathy.

Some studies have reported that angiotensin converting enzyme (ACE) and angiotensinogen (AGT) genes have been associated with hypertrophic cardiomyopathy (HCM). However, there have been inconsonant results among different studies. To clarify the influence of ACE and AGT on HCM, a systemic review and meta-analysis of case-control studies were performed. The following databases were searched to indentify related studies: PubMed database, the Embase database, the Cochrane Central Register of Controlled Trials database, China National Knowledge Information database, and Chinese Scientific and Technological Journal database. Search terms included "hypertrophic cardiomyopathy", "angiotensin converting enzyme" (ACE) or "ACE" and "polymorphism or mutation". For the association of AGT M235T polymorphism and HCM, "angiotensin converting enzyme" or "ACE" was replaced with "angiotensinogen". A total of seventeen studies were included in our review. For the association of ACE I/D polymorphism and HCM, eleven literatures were included in the meta-analysis on association of penetrance and genotype. Similarly, six case-control studies were included in the meta-analysis for AGT M235T. For ACE I/D polymorphism, the comparison of DI/II genotype vs DD genotype was performed in the present meta-analysis. The OR was 0.73 (95% CI: 0.527, 0.998, P = 0.049, power = 94%, alpha = 0.05) after the study which deviated from Hardy-Weinberg Equilibrium was excluded, indicating that the ACE I/D gene polymorphism might be associated with HCM. The AGT M235T polymorphism did not significantly affect the risk of HCM. In addition, ACE I/D gene polymorphism did not significantly influence the interventricular septal thickness in HCM patients. In conclusion, the ACE I/D polymorphism might be associated with the risk of HCM.

Geft is dispensable for the development of the second heart field.

Geft is a guanine nucleotide exchange factor, which can specifically activate Rho family of small GTPase by catalyzing the exchange of bound GDP for GTP. Geft is highly expressed in the excitable tissue as heart and skeletal muscle and plays important roles in many cellular processes, such as cell proliferation, migration, and cell fate decision. However, the in vivo role of Geft remains unknown. Here, we generated a Geft conditional knockout mouse by flanking exons 5-17 of Geft with loxP sites. Cre-mediated deletion of the Geft gene in heart using Mef2c-Cre transgenic mice resulted in a dramatic decrease of Geft expression. Geft knockout mice develop normally and exhibit no discernable phenotype, suggesting Geft is dispensable for the development of the second heart field in mouse. The Geft conditional knockout mouse will be a valuable genetic tool for uncovering the in vivo roles of Geft during development and in adult homeostasis.

Cloning and characterization of the cardiac-specific Lrrc10 promoter.

Leucine-rich repeat containing protein 10 (LRRC10) is characterized as a cardiac-specific gene, suggesting a role in heart development and disease. A severe cardiac morphogenic defect in zebrafish morphants was recently reported but a contradictory result was found in mice, suggesting a more complicated molecular mechanism exists during mouse embryonic development. To elucidate how LRRC10 is regulated, we analyzed the 5'enhancer region approximately 3 kilo bases (kb) upstream of the Lrrc10 start site using luciferase reporter gene assays. Our characterization of the Lrrc10 promoter indicates it possesses complicated cis-and trans-acting elements. We show that GATA4 and MEF2C could both increase transcriptional activity of Lrrc10 promoter individually but that they do not act synergistically, suggesting that there exists a more complex regulation pattern. Surprisingly, knockout of Gata4 and Mef2c binding sites in the 5'enhancer region (-2,894/-2,889) didn't change the transcriptional activity of the Lrrc10 promoter and the likely GATA4 binding site identified was located in a region only 100 base pair (bp) upstream of the promoter. Our data provides insight into the molecular regulation of Lrrc10 expression, which probably also contributes to its tissue-specific expression.

A novel human KRAB-related zinc finger gene ZNF425 inhibits mitogen-activated protein kinase signaling pathway.

Zinc finger (ZNF) proteins play a critical role in cell growth, proliferation, apoptosis, and intracellular signal transduction. In this paper, we cloned and characterized a novel human KRAB-related zinc finger gene, ZNF425, which encodes a protein of 752 amino acids. ZNF425 is strongly expressed in the three month old human embryos and then is almost undetectable in six month old embryos and in adult tissues. An EGFP-ZNF425 fusion protein can be found in both the nucleus and the cytoplasm. ZNF425 appears to act as a transcription repressor. Over-expression of ZNF425 inhibits the transcriptional activities of SRE, AP-1, and SRF. Deletion analysis indicates that the C2H2 domain is the main region responsible for the repression. Our results suggest that the ZNF425 gene is a new transcriptional inhibitor that functions in the MAPK signaling pathway.

The effect of excess expression of GFP in a novel heart-specific green fluorescence zebrafish regulated by nppa enhancer at early embryonic development.

In order to study the impalpable effect of GFP in homozygous heart-specific GFP-positive zebrafish during the early stage, the researchers analyzed the heart function of morphology and physiology at the first 3 days after fertilization. This zebrafish line was produced by a large-scale Tol2 transposon mediated enhancer trap screen that generated a transgenic zebrafish with a heart-specific expression of green fluorescent protein (GFP)-tagged under control of the nppa enhancer. In situ hybridization experiments showed that the nppa:GFP line faithfully recapitulated both the spatial and temporal expressions of the endogenous nppa. Green fluorescence was intensively and specifically expressed in the myocardial cells located both in the heart chambers and in the atrioventricular canal. The embryonic heart of nppa:GFP line developed normally compared with those in the wild type. There was no difference between the nappa:GFP and wild type lines with respect to heart rate, overall size, ejection volume, and fractional shortening. Thus the excess expression of GFP in this transgenic line seemed to exert no detrimental effects on zebrafish hearts during the early stages.

Synergistic efficacy of LBH and alphaB-crystallin through inhibiting transcriptional activities of p53 and p21.

LBH is a transcription factor as a candidate gene for CHD associated with partial trisomy 2p syndrome. To identify potential LBH-interacting partners, a yeast two-hybrid screen using LBH as a bait was performed with a human heart cDNA library. One of the clones identified encodes alphaB-crystallin. Co-immunoprecipitation and GST pull-down assays showed that LBH interacts with alphaB-crystallin, which is further confirmed by mammalian two-hybrid assays. Co-localization analysis showed that in COS-7 cells, alphaB-crystallin that is cytoplasmic alone, accumulates partialy in the nucleus when co-transfected with LBH. Transient transfection assays indicated that overexpression of LBH or alphaB-crystallin reduced the transcriptional activities of p53 and p21, respectively, Overexpression of both alphaB-crystallin and LBH together resulted in a stronger repression of the transcriptional activities of p21 and p53. These results showed that the interaction of LBH and alphaB-crystallin may inhibit synergistically the transcriptional regulation of p53 and p21.

MVP interacts with YPEL4 and inhibits YPEL4-mediated activities of the ERK signal pathway.

Human YPEL4 is a member of YPEL family. It contains a Yippee domain, which is a putative zinc-finger-like, metal-binding domain. The human YPEL4 gene maps to chromosome 11q12.1, is ubiquitously expressed in adult tissues, and encodes a nuclear protein of 127 amino acids, the function of which remains unknown. To gain insights into the cellular function of this protein, we searched for YPEL4-interacting proteins using a yeast two-hybrid screen. The major vault protein (MVP), a lung resistance associated protein, was identified as a binding partner of YPEL4. The interaction between YPEL4 and MVP in mammalian cells was further demonstrated by a series of biochemical assays including the mammalian two-hybrid assay, GST pull-down assay, co-immunoprecipitation assay, and immunocytochemistry. Using a reporter system, we found that MVP can inhibit YPEL4's ability to activate Elk-1 in the MAPK signaling pathway. This study provides new clues for understanding the molecular mechanism of YPEL4 in cell division and signal transduction pathways and should be helpful for understanding molecular functions of the YPEL family.

ZNF552, a novel human KRAB/C2H2 zinc finger protein, inhibits AP-1- and SRE-mediated transcriptional activity.

In this study, we report the identification and characterization of a novel C2H2 zinc finger protein, ZNF552, from a human embryonic heart cDNA library. ZNF552 is composed of three exons and two introns and maps to chromosome 19q13.43. The cDNA of ZNF552 is 2.3 kb, encoding 407 amino acids with an amino-terminal KRAB domain and seven carboxyl-terminal C2H2 zinc finger motifs in the nucleus and cytoplasm. Northern blotting analysis indicated that a 2.3 kb transcript specific for ZNF552 was expressed in liver, lung, spleen, testis and kidney, especially with a higher level in the lung and testis in human adult tissues. Reporter gene assays showed that ZNF552 was a transcriptional repressor, and overexpression of ZNF552 in the COS-7 cells inhibited the transcriptional activities of AP-1 and SRE, which could be relieved through RNAi analysis. Deletion studies showed that the KRAB domain of ZNF552 may be involved in this inhibition.