Crucial Roles of MZF1 and Sp1 in the Transcriptional Regulation of the Peptidylarginine Deiminase Type I Gene (PADI1) in Human Keratinocytes

Peptidyl Arginine Deiminases in Chronic Diseases: A Focus on Rheumatoid Arthritis and Interstitial Lung Disease

Protein citrullination is accomplished by a broad enzyme family named Peptidyl Arginine Deiminases (PADs), which makes this post-translational modification in many proteins that perform physiological and pathologic mechanisms in the body. Due to these modifications, citrullination has become a significant topic in the study of pathological processes. It has been related to some chronic and autoimmune diseases, including rheumatoid arthritis (RA), interstitial lung diseases (ILD), multiple sclerosis (MS), and certain types of cancer, among others. Antibody production against different targets, including filaggrin, vimentin, and collagen, results in an immune response if they are citrullinated, which triggers a continuous inflammatory process characteristic of autoimmune and certain chronic diseases. PAD coding genes (PADI1 to PADI4 and PADI6) harbor variations that can be important in these enzymes' folding, activity, function, and half-life. However, few studies have considered these genetic factors in the context of chronic diseases. Exploring PAD pathways and their role in autoimmune and chronic diseases is a major topic in developing new pharmacological targets and valuable biomarkers to improve diagnosis and prevention. The present review addresses and highlights genetic, molecular, biochemical, and physiopathological factors where PAD enzymes perform a major role in autoimmune and chronic diseases.

Deimination in epidermal barrier and hair formation

Peptidylarginine deiminases (PADs) transform a protein arginine residue into the non-standard amino acid citrulline. This calcium-dependent post-translational modification of proteins is called citrullination or deimination. As described in this special issue, PADs play a role in various physiological processes, and PAD deregulations are involved in many human diseases. Three PADs are expressed in the epidermis, where their roles begin to be deciphered. PAD1 and PAD3 are involved in keratinocyte differentiation, particularly in the epidermal barrier function, keratins, filaggrin and filaggrin-related proteins being the most abundant deiminated epidermal proteins. Reduced amounts of deiminated proteins and PAD1 expression may be involved in the pathogenesis of psoriasis and atopic dermatitis, two very frequent and chronic skin inflammatory diseases. The trichohyalin/PAD3/transglutaminase three pathway is important for hair shaft formation. Mutations of the PADI3 gene, leading to a decreased activity or abnormal localization of the corresponding isotype, are the cause of a rare hair disorder called uncombable hair syndrome, and are associated with the central centrifugal cicatricial alopecia, a frequent alopecia mainly affecting women of African ancestry. This article is part of the Theo Murphy meeting issue 'The virtues and vices of protein citrullination'.

Genetic association of wool quality characteristics in United States Rambouillet sheep

Introduction: Fine wool production is an important source of revenue, accounting for up to 13% of total revenue in extensively managed wool sheep production systems of the United States. The Rambouillet are a predominant breed that excels in wool quality characteristics. Understanding the genetic basis of wool quality characteristics would aid in the development of genomic breeding strategies to facilitate genetic improvement. Methods: Wool characteristics and DNA were collected for rams enrolled in the North Dakota State University and University of Wyoming annual central performance ram tests over a three-year period (2019-2021, N = 313). The relationships of wool quality characteristics including grease fleece weight adjusted 365 days (wt. 365 adj.), clean fleece wt. 365 adj., staple length 365 adj., average fiber diameter, face wool cover, amount of skin wrinkles and belly wool were evaluated through genome-wide association studies (GWAS), Pearson correlation and ANOVA. Results: The GWAS identified four genome-wide significant genetic markers (p-value <1.19e-06) and five chromosome-wide significant markers (p-value <1.13e-05) on chromosomes 1, 2, 4, 15, and 19. Significant markers were associated with genes notable for relevant wool biological functions, including the gene ABCC8 which codes for SUR1, an ATP-sensitive potassium channel known to affect hair growth and 60S ribosomal protein L17-like, previously found to be expressed during follicle formation. The strongest Pearson correlation coefficients were identified between clean fleece wt. 365 adj. and grease fleece wt. 365 adj. (r = 0.83) and between clean fleece wt. 365 adj. and staple length 365 adj. (r = 0.53). Additionally, clean fleece wt. 365 adj. was correlated with final body weight (r = 0.35) and scrotal circumference (r = 0.16). Staple length 365 adj. (p-value = 5e-04), average fiber diameter (p-value = .0053) and clean fleece wt. 365 adj. (p-value = .014) were significantly associated with belly wool score. Discussion: The results of this study provide important insight into the relationships between wool quality characteristics and report specific markers that Rambouillet sheep producers may use to help inform selection and breeding decisions for improved wool quality.

Role of the PADI family in inflammatory autoimmune diseases and cancers: A systematic review

The peptidyl arginine deiminase (PADI) family is a calcium ion-dependent group of isozymes with sequence similarity that catalyze the citrullination of proteins. Histones can serve as the target substrate of PADI family isozymes, and therefore, the PADI family is involved in NETosis and the secretion of inflammatory cytokines. Thus, the PADI family is associated with the development of inflammatory autoimmune diseases and cancer, reproductive development, and other related diseases. In this review, we systematically discuss the role of the PADI family in the pathogenesis of various diseases based on studies from the past decade to provide a reference for future research.

Skin Minerals: Key Roles of Inorganic Elements in Skin Physiological Functions

As odd as it may seem at first glance, minerals, it is what we are all about…or nearly. Although life on Earth is carbon-based, several other elements present in the planet’s crust are involved in and often indispensable for functioning of living organisms. Many ions are essential, and others show supportive and accessory qualities. They are operative in the skin, supporting specific processes related to the particular situation of this organ at the interface with the environment. Skin bioenergetics, redox balance, epidermal barrier function, and dermal remodeling are amongst crucial activities guided by or taking advantage of mineral elements. Skin regenerative processes and skin ageing can be positively impacted by adequate accessibility, distribution, and balance of inorganic ions.

Construction of a novel gene-based model for prognosis prediction of clear cell renal cell carcinoma

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) comprises the majority of kidney cancer death worldwide, whose incidence and mortality are not promising. Identifying ideal biomarkers to construct a more accurate prognostic model than conventional clinical parameters is crucial.

METHODS

Raw count of RNA-sequencing data and clinicopathological data were acquired from The Cancer Genome Atlas (TCGA). Tumor samples were divided into two sets. Differentially expressed genes (DEGs) were screened in the whole set and prognosis-related genes were identified from the training set. Their common genes were used in LASSO and best subset regression which were performed to identify the best prognostic 5 genes. The gene-based risk score was developed based on the Cox coefficient of the individual gene. Time-dependent receiver operating characteristic (ROC) and Kaplan-Meier (KM) survival analysis were used to assess its prognostic power. GSE29609 dataset from GEO (Gene Expression Omnibus) database was used to validate the signature. Univariate and multivariate Cox regression were performed to screen independent prognostic parameters to construct a nomogram. The predictive power of the nomogram was revealed by time-dependent ROC curves and the calibration plot and verified in the validation set. Finally, Functional enrichment analysis of DEGs and 5 novel genes were performed to suggest the potential biological pathways.

RESULTS

PADI1, ATP6V0D2, DPP6, C9orf135 and PLG were screened to be significantly related to the prognosis of ccRCC patients. The risk score effectively stratified the patients into high-risk group with poor overall survival (OS) based on survival analysis. AJCC-stage, age, recurrence and risk score were regarded as independent prognostic parameters by Cox regression analysis and were used to construct a nomogram. Time-dependent ROC curves showed the nomogram performed best in 1-, 3- and 5-year survival predictions compared with AJCC-stage and risk score in validation sets. The calibration plot showed good agreement of the nomogram between predicted and observed outcomes. Functional enrichment analysis suggested several enriched biological pathways related to cancer.

CONCLUSIONS

In our study, we constructed a gene-based model integrating clinical prognostic parameters to predict prognosis of ccRCC well, which might provide a reliable prognosis assessment tool for clinician and aid treatment decision-making in the clinic.

Beta-caryophyllene enhances wound healing through multiple routes

Beta-caryophyllene is an odoriferous bicyclic sesquiterpene found in various herbs and spices. Recently, it was found that beta-caryophyllene is a ligand of the cannabinoid receptor 2 (CB2). Activation of CB2 will decrease pain, a major signal for inflammatory responses. We hypothesized that beta-caryophyllene can affect wound healing by decreasing inflammation. Here we show that cutaneous wounds of mice treated with beta-caryophyllene had enhanced re-epithelialization. The treated tissue showed increased cell proliferation and cells treated with beta-caryophyllene showed enhanced cell migration, suggesting that the higher re-epithelialization is due to enhanced cell proliferation and cell migration. The treated tissues also had up-regulated gene expression for hair follicle bulge stem cells. Olfactory receptors were not involved in the enhanced wound healing. Transient Receptor Potential channel genes were up-regulated in the injured skin exposed to beta-caryophyllene. Interestingly, there were sex differences in the impact of beta- caryophyllene as only the injured skin of female mice had enhanced re-epithelialization after exposure to beta-caryophyllene. Our study suggests that chemical compounds included in essential oils have the capability to improve wound healing, an effect generated by synergetic impacts of multiple pathways.

Nonclinical and human pharmacology of the potent and selective topical retinoic acid receptor-γ agonist trifarotene

BACKGROUND

First- and third-generation retinoids are the main treatment for acne. Even though efficacious, they lack full selectivity for retinoic acid receptor (RAR) γ, expressed in the epidermis and infundibulum.

OBJECTIVES

To characterize the in vitro metabolism and the pharmacology of the novel retinoid trifarotene.

MATERIALS AND METHODS

In vitro assays determined efficacy, potency and selectivity on RARs, as well as the activity on the expression of retinoid target genes in human keratinocytes and ex vivo cultured skin. In vivo studies investigated topical comedolytic, anti-inflammatory and depigmenting properties. The trifarotene-induced gene expression profile was investigated in nonlesional skin of patients with acne and compared with ex vivo and in vivo models. Finally, the metabolic stability in human keratinocytes and hepatic microsomes was established.

RESULTS

Trifarotene is a selective RARγ agonist with > 20-fold selectivity over RARα and RARβ. Trifarotene is active and stable in keratinocytes but rapidly metabolized by human hepatic microsomes, predicting improved safety. In vivo, trifarotene 0·01% applied topically is highly comedolytic and has anti-inflammatory and antipigmenting properties. Gene expression studies indicated potent activation of known retinoid-modulated processes (epidermal differentiation, proliferation, stress response, retinoic acid metabolism) and novel pathways (proteolysis, transport/skin hydration, cell adhesion) in ex vivo and in vivo models, as well as in human skin after 4 weeks of topical application of trifarotene 0·005% cream.

CONCLUSIONS

Based on its RARγ selectivity, rapid degradation in human hepatic microsomes and pharmacological properties including potent modulation of epidermal processes, topical treatment with trifarotene could result in good efficacy and may present a favourable safety profile in acne and ichthyotic disorders.

Peptidylarginine deiminases and deiminated proteins at the epidermal barrier

Deimination or citrullination is a post-translational modification catalysed by a family of calcium-dependent enzymes called peptidylarginine deiminases (PADs). It corresponds to the transformation of arginine residues within a peptide sequence into citrulline residues. Deimination induces a decreased net charge of targeted proteins; therefore, it alters their folding and changes intra- and intermolecular ionic interactions. Deimination is involved in several physiological processes (inflammation, gene regulation, etc.) and human diseases (rheumatoid arthritis, neurodegenerative diseases, cancer, etc.). Here, we describe the PADs expressed in the epidermis and their known substrates, focusing on their role in the epidermal barrier function.

Characteristics and Expression Profile of KRT71 Screened by Suppression Subtractive Hybridization cDNA Library in Curly Fleece Chinese Tan Sheep

As an important commercial trait for sheep, curly fleece has a great economic impact on production costs and efficiency in sheep industry. To identify genes that are important for curly fleece formation in mammals, a suppression subtractive hybridization analysis was performed on the shoulder skin tissues exposed to two different growth stages of Chinese Tan sheep with different phenotypes (curly fleece and noncurling fleece). BLAST analysis identified 67 differentially expressed genes, of which 31 were expressed lower and 36 were expressed higher in lambs than in adult sheep. Differential expressions of seven randomly selected genes were verified using quantitative real-time polymerase chain reaction (qRT-PCR). KRT71 gene was selected for further study due to its high correlation with the curly hair phenotype in various mammal species. Semi-qPCR showed distinctively high expression of KRT71 in skin tissues. Moreover, qPCR result showed a significantly higher expression of KRT71 in curly fleece than noncurling Tan sheep. The luciferase assay and electrophoresis mobility shift assay showed that there were transcription factor binding sites in the promoter region of KRT71 related to the differential expression of KRT71 at the two growth stages of Tan sheep. Online bioinformation tools predicted MFZ1 as a transcriptional factor that regulates the expression of KRT71. These studies on KRT71 gene revealed some mechanisms underlying the relationship between the KRT71 gene and the curly fleece phenotype of Tan sheep.

Peptidylarginine deiminase 1-catalyzed histone citrullination is essential for early embryo development

Peptidylarginine deiminase (PADI) enzymes are increasingly being associated with the regulation of chromatin structure and gene activity via histone citrullination. As one of the PADI family members, PADI1 has been mainly reported to be expressed in the epidermis and uterus, where the protein in keratinocytes is thought to promote differentiation by citrullinating filament proteins. However, the roles of PADI1 in preimplantation development have not been addressed. Using a PADI1-specific inhibitor and Padi1-morpholino knockdown, we found that citrullination of histone tails at H4R3 and H3R2/8/17 were markedly reduced in the 2- and 4-cell embryos. Consistent with this observation, early embryo development was also arrested at the 4-cell stage upon depletion of PADI1 or inhibition of PADI1 enzyme activity. Additionally, by employing 5-ethynyl uridine (EU) incorporation analysis, ablation of PADI1 function led to a dramatic decrease in overall transcriptional activity, correlating well with the reduced levels of phosphorylation of RNA Pol II at Ser2 observed at 2- or 4-cell stage of embryos under Padi1 knockdown or inhibiting PADI1. Thus, our data reveal a novel function of PADI1 during early embryo development transitions by catalyzing histone tail citrullination, which facilitates early embryo genome transactivation.

Characterization of the porcine peptidylarginine deiminase type VI gene (PADI6) promoter: Sp1 regulates basal transcription of the porcine PADI6

It is a general consensus that oocyte quality is the key to embryo survival in pig reproduction. Thus, study on regulation of the ovary-associated gene is of great significance in pig breeding. Peptidylarginine deiminases (PADs) are a family of enzymes which catalyze the conversion of arginine to citrulline in proteins. The peptidylarginine deiminases type VI gene (PADI6) is mainly expressed in the ovary, and plays an important role in oocyte growth, fertilization and early embryo development. However, until now, little is known about its transcriptional regulation mechanism. Here, we firstly isolated and characterized the 5'-flanking region of porcine PADI6 gene. We determined the transcription start site using 5'-rapid amplification of cDNA ends (RACE) analysis, and identified the minimal promoter (-85/+68) that drove the basal expression of PADI6 by constructing various progressive deletions. Mutational analysis and electrophoretic mobility shift assays demonstrated Sp1 bound to the -56/-47 region of the PADI6 promoter. Furthermore, overexpression of Sp1 significantly increased the promoter activity and promoted PADI6 gene expression, and accordingly, inhibition of Sp1 expression with specific siRNA significantly reduced the promoter activity and suppressed the PADI6 expression. In addition, inhibition of Sp1 binding by Mithramycin A treatment reduced the transcriptional activity of PADI6 in a dose-dependent manner. Taken together, these data indicate that Sp1 is essential for the transcriptional regulation of PADI6.

Identification and analysis of the promoter region of the human HAS3 gene

Hyaluronan (HA) is a key component of the vertebrate extracellular matrix that is synthesized at the plasma membrane by the hyaluronan synthases including HAS1, HAS2 and HAS3. The expression and regulation of HAS1-3 are implicated in numerous physiological and pathological processes. The promoters of human HAS1 and HAS2 genes have been identified previously whereas HAS3 promoter remains unclear. In the present study, we have for the first time identified and characterized the human HAS3 gene promoter region. 5' RACE assay revealed two novel transcriptional variants of HAS3 gene with distinct transcription start sites. Progressive deletion analysis of the 5'-flanking region of HAS3 gene demonstrated that HAS3 proximal promoter is mainly restricted to a 450-bp region (i.e. -761 to -305 bp upstream of the major HAS3 transcription start site), whereas its core promoter is located to a minimal 129-bp region (i.e. -433 to -305 bp upstream of the major HAS3 transcription start site). Transcriptional factor binding analysis indicated that HAS3 gene promoter lacks of canonical TATA box, but contains classical GC box as well as other putative binding sites for transcriptional factors such as C/EBP and NFκB. In addition, site-directed mutagenesis assay demonstrated that the proximal Sp1 binding site is essential for the robust proximal promoter activity of HAS3 gene whereas the core MTE (core promoter motif ten elements) motif is required for the basic core promoter activity of HAS3 gene. Our present study should facilitate further studies on the mechanism regulating the expression of this important gene.

Transcriptional regulation of heterogeneous nuclear ribonucleoprotein K gene expression

Heterogeneous nuclear ribonucleoprotein K (hnRNP K) is importantly involved in the regulation of development, DNA damage response, and several human diseases. The molecular mechanisms that control the expression of hnRNP K are largely unknown. In the present study, we investigated the detailed mechanism of the transcriptional regulation of human hnRNP K gene. Two activating and one repressive elements located in the proximal segment of the transcriptional initiation site were identified in hnRNP K gene. A 19 bp-region was responsible for the inhibitory activities of the repressor element. Twenty proteins were identified by DNA-affinity purification and mass spectrometry analyses as binding partners of the primary activating element in the hnRNP K promoter. Chromatin immunoprecipitation and EMSA analysis confirmed the binding of Sp1 with hnRNP K promoter. Sp1 enhanced the promoter activity, increased the expression of hnRNP K, and reduced the mRNA level of angiotensinogen, a gene known to be negatively regulated by hnRNP K. In summary, the current study characterized the promoter elements that regulate the transcription of human hnRNP K gene, identified 20 proteins that bind to the primary activating element of hnRNP K promoter, and demonstrated a functional effect of Sp1 on hnRNP K transcription.

Bleomycin hydrolase is regulated biphasically in a differentiation- and cytokine-dependent manner: relevance to atopic dermatitis

Loss-of-function mutation in the profilaggrin gene is a major risk factor for atopic dermatitis (AD). Previously, we showed that a neutral cysteine protease, bleomycin hydrolase (BH), has a role in generating natural moisturizing factors, and calpain I is an upstream protease in the filaggrin degradation pathway. Here, we investigated the transcriptional regulatory mechanisms of BH and the relevance of BH to AD. First, we cloned the 5'-flanking region of BH. Deletion analyses identified a critical region for BH promoter activity within -216 bp upstream. Electrophoretic mobility shift assay revealed that MZF-1, Sp-1, and interferon regulatory factor-1/2 could bind to this region in vitro. Moreover, site-directed mutagenesis of the MZF-1 and Sp-1 motifs markedly reduced BH promoter activity. These data indicate that BH expression is up-regulated via MZF-1 and Sp-1. Interestingly, a Th1 cytokine, IFN-γ, significantly reduced the expression of BH. Analyses with site-directed mutagenesis and small interference RNA supported the suppressing effect of IFN-γ on BH expression. On the other hand, a Th2 cytokine, IL-4, did not show any direct effect on BH expression. However, it down-regulated MZF-1 and Sp-1 in cultured keratinocytes, indicating that IL-4 could work as a suppressor in BH regulation. Lastly, we examined expression of BH in skins of patients with AD. BH activity and expression were markedly decreased in AD lesional skin, suggesting a defect of the filaggrin degradation pathway in AD. Our results suggest that BH transcription would be modulated during both differentiation and inflammation.

An intronic enhancer driven by NF-κB contributes to transcriptional regulation of peptidylarginine deiminase type I gene in human keratinocytes

Peptidylarginine deiminases (PADs) catalyze the conversion of protein-bound arginine to citrulline residues. In human epidermis, where filaggrin is the main deiminated protein, three PADs are detected with specific patterns of expression depending on the keratinocyte (KC) differentiation state. Previous characterizations of the PAD-encoding gene promoters have shown that proximal regulation alone is not sufficient to explain this specificity of expression. In this work, we describe an evolutionarily highly conserved nucleotide segment located in the first intron of the PAD1 gene (PADI1). Luciferase reporter assays showed that it enhances the activity of the PADI1 promoter, in a calcium- and orientation-independent manner. Mutation of a putative NF-κB cis-element markedly reduced its enhancer activity, which also confirmed its potential regulatory function. Chromatin immunoprecipitation assays evidenced the binding of both p65 and p50 NF-κB subunits to the cis-element, and RNA interference inhibition assays confirmed that NF-κB contributes to the PADI1 transcriptional control. Furthermore, the intronic enhancer and promoter of PADI1 potentially interact through chromatin looping, as indicated by chromosome conformation capture assays. Our findings provide evidence that an NF-κB-mediated signaling pathway is involved in PADI1 regulation in human epidermal KCs.

Deimination is regulated at multiple levels including auto-deimination of peptidylarginine deiminases

Peptidylarginine deiminases (PADs) catalyze deimination, converting arginyl to citrullyl residues. Only three PAD isotypes are detected in the epidermis where they play a crucial role, targeting filaggrin, a key actor for the tissue hydration and barrier functions. Their expression and activation depends on the keratinocyte differentiation state. To investigate this regulation, we used primary keratinocytes induced to differentiate either by increasing cell-density or by treatment with vitamin D. High cell-density increased PAD1 and 3, but not PAD2, at the mRNA and protein levels, and up-regulated protein deimination. By contrast, vitamin D increased PAD1-3 mRNA amounts, with distinct kinetics, but neither the proteins nor the deimination rate. Furthermore, auto-deimination was shown to decrease PAD activity, increasing the distances between the four major amino acids of the active site. In summary, deimination can be regulated at multiple levels: transcription of the PADI genes, translation of the corresponding mRNAs, and auto-deimination of PADs.

Myeloid zinc finger 1 induces migration, invasion, and in vivo metastasis through Axl gene expression in solid cancer

Myeloid zinc finger 1 (MZF1) is a member of the SCAN domain family transcription factors that form dimers through their highly conserved SCAN motifs. Silencing of MZF1 inhibits cell proliferation, and abnormal expression of MZF1 results in cancer development. However, a potential role of MZF1 in metastasis remains unclear. Axl is a receptor tyrosine kinase and was first identified as a transforming gene in chronic myeloid leukemia. Axl overexpression induces proliferation, migration, and invasion and is highly expressed in different human cancers. In this study, we show that overexpression of MZF1 induces migration and invasion in colorectal (Rko, SW480) and cervical (HeLa) cancer cells. In addition, we show that MZF1 binds to the Axl promoter, transactivates promoter activity, and enhances Axl-mRNA and protein expression in a dose-dependent manner. In vitro, sh-RNA knockdown of Axl reduced MZF1-induced migration and invasion in HeLa and Rko cells (P = 0.05). Additionally, Rko cells overexpressing MZF1 showed increased tumor formation and liver metastasis in the chicken-embryo-metastasis assay in vivo. Furthermore, the expression of MZF1 and Axl was significantly higher in resected colorectal tumors compared with corresponding normal tissues (P = 0.02; P = 0.05), and MZF1 expression was positively correlated with Axl gene expression in tumor tissues (P < 0.01). Taken together, this is the first study to show that MZF1 induces invasion and in vivo metastasis in colorectal and cervical cancer, at least in part by regulating Axl gene expression.

Cloning and analysis of rat osteoclast inhibitory lectin gene promoter

Osteoclast inhibitory lectin (OCIL) is a novel regulator of bone remodeling, however, little is known concerning how OCIL is regulated to date. In this study, approximately 4.4 kb of the 5'-flanking sequence of rat OCIL gene was cloned into the promoter-less reporter vector pGL3-basic and transiently transfected into three different cell lines. The differences in the levels of luciferase activity paralleled well with the levels of OCIL mRNA expression in these cells, suggesting that the regulation of rat OCIL gene expression occurs mainly at the transcriptional level. Additional luciferase assays using a series of constructs containing unidirectionally deleted fragments showed that the construct-1819/pGL3 (-1819 to +118) exhibited the highest luciferase activity, suggesting the presence of functional promoter in this region. The region from -4370 to -2805 might contain negative regulatory elements, while the region from -1819 to -1336 might have important positive regulatory elements that enhance OCIL transcription. Sequence analysis of the promoter revealed the absence of both TATA and CAAT boxes. However, in the proximal promoter region (-81 to +118), several potential transcription factor binding sites that may be responsible for the basal transcriptional activity of rat OCIL promoter were observed. The promoter contains several potential Sp1 binding sites, and cotransfection of a shRNA expression plasmid that knockdowns Sp1 significantly reduced OCIL promoter activity and endogenous gene expression and moreover, overexpressing Sp7, a Sp1 family member that also binds to Sp1 binding sequence, increased OCIL promoter activity and gene expression, suggesting a role of Sp1 family proteins in regulation of OCIL transcription.

Long-range enhancer associated with chromatin looping allows AP-1 regulation of the peptidylarginine deiminase 3 gene in differentiated keratinocyte

Transcription control at a distance is a critical mechanism, particularly for contiguous genes. The peptidylarginine deiminases (PADs) catalyse the conversion of protein-bound arginine into citrulline (deimination), a critical reaction in the pathophysiology of multiple sclerosis, Alzheimer's disease and rheumatoid arthritis, and in the metabolism of the major epidermal barrier protein filaggrin, a strong predisposing factor for atopic dermatitis. PADs are encoded by 5 clustered PADI genes (1p35-6). Unclear are the mechanisms controlling the expression of the gene PADI3 encoding the PAD3 isoform, a strong candidate for the deimination of filaggrin in the terminally differentiating epidermal keratinocyte. We describe the first PAD Intergenic Enhancer (PIE), an evolutionary conserved non coding segment located 86-kb from the PADI3 promoter. PIE is a strong enhancer of the PADI3 promoter in Ca2+-differentiated epidermal keratinocytes, and requires bound AP-1 factors, namely c-Jun and c-Fos. As compared to proliferative keratinocytes, calcium stimulation specifically associates with increased local DNase I hypersensitivity around PIE, and increased physical proximity of PIE and PADI3 as assessed by Chromosome Conformation Capture. The specific AP-1 inhibitor nordihydroguaiaretic acid suppresses the calcium-induced increase of PADI3 mRNA levels in keratinocytes. Our findings pave the way to the exploration of deimination control during tumorigenesis and wound healing, two conditions for which AP-1 factors are critical, and disclose that long-range transcription control has a role in the regulation of the gene PADI3. Since invalidation of distant regulators causes a variety of human diseases, PIE results to be a plausible candidate in association studies on deimination-related disorders or atopic disease.

Long-range enhancer differentially regulated by c-Jun and JunD controls peptidylarginine deiminase-3 gene in keratinocytes

Long-range cis elements are critical regulators of transcription, particularly for clustered paralogous genes. Such are the five PADI genes in 1p35-36 encoding peptidylarginine deiminases, which catalyze deimination, a Ca2+-dependent post-translational modification. Deimination has been implicated in the pathophysiology of severe human diseases such as multiple sclerosis and rheumatoid arthritis. The PADI genes present different expression patterns. PADI1-3 are expressed in the epidermis, with increased expression levels in the most differentiated keratinocytes. Previous studies on PADI proximal promoters failed to explain such specificity of expression. We identified a conserved intergenic sequence in the PADI locus (IG1), which may play a role in PADI transcriptional regulation. In this work, we identified two DNase I.hypersensitive sites located in IG1, PAD intergenic enhancer segment 1 (PIE-S1) and PIE-S2, which act in synergy as a bipartite enhancer of the PADI3 and probably PADI1 promoters in normal human epidermal keratinocytes differentiated by a high-calcium-containing medium (1.5 mM). PIE-S1 and PIE-S2 present all the hallmarks of transcriptional enhancers: orientation-independence, copy-number dependence and cell-type specificity. PIE-S1 and PIE-S2 comprise conserved putative binding sites for MIBP1/RFX1 and activator protein 1, respectively. Deletion mutant screening revealed that these sites are crucial for the enhancer activity. Furthermore, chromatin immunoprecipitation assays evidenced differential binding of JunD or c-Jun on the activator protein 1 site depending on the cell differentiation state. Our results reveal the molecular bases of the expression specificity of PADI1 and PADI3 during keratinocyte differentiation through a long-range enhancer and support a model of PADI gene regulation depending on c-Jun-JunD competition.

Myeloid cell differentiation in response to calcitriol for expression CD11b and CD14 is regulated by myeloid zinc finger-1 protein downstream of phosphatidylinositol 3-kinase

Immature cells of the mononuclear phagocyte series differentiate in response to calcitriol. This is accompanied by increased expression of both CD11b and CD14 and has been shown to be phosphatidylinositol 3-kinase (PI3K) dependent. The events downstream of PI3K that regulate mononuclear phagocyte gene expression, however, remain to be fully understood. In the present study, we show that incubation of THP-1 cells with calcitriol brings about activation of the myeloid zinc finger-1 (MZF-1) transcription factor dependent upon PI3K. In addition, we show that the proximal promoter regions of both CD11b and CD14 contain functional MZF-1 binding sites that are calcitriol responsive. Site-directed mutagenesis of the putative MZF-1 elements abolished MZF-1 binding to the promoters of both CD11b and CD14. Not only did calcitriol treatment increase MZF-1 DNA binding activity to these sites, but it also up-regulated cellular levels of MZF-1. Silencing of MZF-1 resulted in a markedly blunted response to calcitriol for induction of both CD11b and CD14 mRNA transcript levels. Cell surface expression of CD11b and CD14 was also reduced, but to a lesser extent. Taken together, these results show that MZF-1 is involved downstream of PI3K in a calcitriol-induced signaling pathway leading to myeloid cell differentiation and activation of CD11b and CD14.