Basonuclin regulates a subset of ribosomal RNA genes in HaCaT cells

The SUMOylation pathway regulates the pathogenicity of Fusarium oxysporum f. sp. niveum in watermelon through stabilizing the pH regulator FonPalC via SUMOylation

SUMOylation is a key post-translational modification, where small ubiquitin-related modifier (SUMO) proteins regulate crucial biological processes, including pathogenesis, in phytopathogenic fungi. Here, we investigated the function and mechanism of the SUMOylation pathway in the pathogenicity of Fusarium oxysporum f. sp. niveum (Fon), the fungal pathogen that causes watermelon Fusarium wilt. Disruption of key SUMOylation pathway genes, FonSMT3, FonAOS1, FonUBC9, and FonMMS21, significantly reduced pathogenicity, impaired penetration ability, and attenuated invasive growth capacity of Fon. Transcription and proteomic analyses identified a diverse set of SUMOylation-regulated differentially expressed genes and putative FonSMT3-targeted proteins, which are predicted to be involved in infection, DNA damage repair, programmed cell death, reproduction, growth, and development. Among 155 putative FonSMT3-targeted proteins, FonPalC, a Pal/Rim-pH signaling regulator, was confirmed to be SUMOylated. The FonPalC protein accumulation was significantly decreased in SUMOylation-deficient mutant ∆Fonsmt3. Deletion of FonPalC resulted in impaired mycelial growth, decreased pathogenicity, enhanced osmosensitivity, and increased intracellular vacuolation in Fon. Importantly, mutations in conserved SUMOylation sites of FonPalC failed to restore the defects in ∆Fonpalc mutant, indicating the critical function of the SUMOylation in FonPalC stability and Fon pathogenicity. Identifying key SUMOylation-regulated pathogenicity-related proteins provides novel insights into the molecular mechanisms underlying Fon pathogenesis regulated by SUMOylation.

BNC1 deficiency induces mitochondrial dysfunction-triggered spermatogonia apoptosis through the CREB/SIRT1/FOXO3 pathway: the therapeutic potential of nicotinamide riboside and metformin†

Male infertility is a global health problem that disturbs numerous couples worldwide. Basonuclin 1 (BNC1) is a transcription factor mainly expressed in proliferative keratinocytes and germ cells. A frameshift mutation of BNC1 was identified in a large Chinese primary ovarian insufficiency pedigree. The expression of BNC1 was significantly decreased in the testis biopsies of infertile patients with nonobstructive azoospermia. Previous studies have revealed that mice with BNC1 deficiency are generally subfertile and undergo gradual spermatogenic failure. We observed that apoptosis of spermatogonia is tightly related to spermatogenic failure in mice with a Bnc1 truncation mutation. Such impairment is related to mitochondrial dysfunction causing lower mitochondrial membrane potential and higher reactive oxygen species. We showed that downregulation of CREB/SIRT1/FOXO3 signaling participates in the above impairment. Administration of nicotinamide riboside or metformin reversed mitochondrial dysfunction and inhibited apoptosis in Bnc1-knockdown spermatogonia by stimulating CREB/SIRT1/FOXO3 signaling. Dietary supplementation with nicotinamide riboside or metformin in mutated mice increased SIRT1 signaling, improved the architecture of spermatogenic tubules, inhibited apoptosis of the testis, and improved the fertility of mice with a Bnc1 truncation mutation. Our data establish that oral nicotinamide riboside or metformin can be useful for the treatment of spermatogenic failure induced by Bnc1 mutation.

PRMT1 Inhibition Selectively Targets BNC1-Dependent Proliferation, but not Migration in Squamous Cell Carcinoma

Squamous Cell Carcinoma (SCC) develops in stratified epithelial tissues and demonstrates frequent alterations in transcriptional regulators. We sought to discover SCC-specific transcriptional programs and identified the transcription factor Basonuclin 1 (BNC1) as highly expressed in SCC compared to other tumor types. RNA-seq and ChIP-seq analysis identified pro-proliferative genes activated by BNC1 in SCC cells and keratinocytes. Inhibition of BNC1 in SCC cells suppressed proliferation and increased migration via FRA1. In contrast, BNC1 reduction in keratinocytes caused differentiation, which was abrogated by IRF6 knockdown, leading to increased migration. Protein interactome analysis identified PRMT1 as a co-activator of BNC1-dependent proliferative genes. Inhibition of PRMT1 resulted in a dose-dependent reduction in SCC cell proliferation without increasing migration. Importantly, therapeutic inhibition of PRMT1 in SCC xenografts significantly reduced tumor size, resembling functional effects of BNC1 knockdown. Together, we identify BNC1-PRMT1 as an SCC-lineage specific transcriptional axis that promotes cancer growth, which can be therapeutically targeted to inhibit SCC tumorigenesis.

Single human oocyte transcriptome analysis reveals distinct maturation stage-dependent pathways impacted by age

Female fertility is inversely correlated with maternal age due to a depletion of the oocyte pool and a reduction in oocyte developmental competence. Few studies have addressed the effect of maternal age on the human mature oocyte (MII) transcriptome, which is established during oocyte growth and maturation, however, the pathways involved remain unclear. Here, we characterize and compare the transcriptomes of a large cohort of fully grown germinal vesicle stage (GV) and in vitro matured (IVM‐MII) oocytes from women of varying reproductive age. First, we identified two clusters of cells reflecting the oocyte maturation stage (GV and IVM‐MII) with 4445 and 324 putative marker genes, respectively. Furthermore, we identified genes for which transcript representation either progressively increased or decreased with age. Our results indicate that the transcriptome is more affected by age in IVM‐MII oocytes (1219 genes) than in GV oocytes (596 genes). In particular, we found that transcripts of genes involved in chromosome segregation and RNA splicing significantly increased representation with age, while genes related to mitochondrial activity showed a lower representation. Gene regulatory network analysis facilitated the identification of potential upstream master regulators of the genes involved in those biological functions. Our analysis suggests that advanced maternal age does not globally affect the oocyte transcriptome at GV or IVM‐MII stages. Nonetheless, hundreds of genes displayed altered transcript representation, particularly in IVM‐MII oocytes, which might contribute to the age‐related quality decline in human oocytes.

Repression of interrupted and intact rDNA by the SUMO pathway in Drosophila melanogaster

Ribosomal RNAs (rRNAs) are essential components of the ribosome and are among the most abundant macromolecules in the cell. To ensure high rRNA level, eukaryotic genomes contain dozens to hundreds of rDNA genes, however, only a fraction of the rRNA genes seems to be active, while others are transcriptionally silent. We found that individual rDNA genes have high level of cell-to-cell heterogeneity in their expression in Drosophila melanogaster. Insertion of heterologous sequences into rDNA leads to repression associated with reduced expression in individual cells and decreased number of cells expressing rDNA with insertions. We found that SUMO (Small Ubiquitin-like Modifier) and SUMO ligase Ubc9 are required for efficient repression of interrupted rDNA units and variable expression of intact rDNA. Disruption of the SUMO pathway abolishes discrimination of interrupted and intact rDNAs and removes cell-to-cell heterogeneity leading to uniformly high expression of individual rDNA in single cells. Our results suggest that the SUMO pathway is responsible for both repression of interrupted units and control of intact rDNA expression.

Frequent Germline and Somatic Single Nucleotide Variants in the Promoter Region of the Ribosomal RNA Gene in Japanese Lung Adenocarcinoma Patients

Ribosomal RNA (rRNA), the most abundant non-coding RNA species, is a major component of the ribosome. Impaired ribosome biogenesis causes the dysfunction of protein synthesis and diseases called “ribosomopathies,” including genetic disorders with cancer risk. However, the potential role of rRNA gene (rDNA) alterations in cancer is unknown. We investigated germline and somatic single-nucleotide variants (SNVs) in the rDNA promoter region (positions −248 to +100, relative to the transcription start site) in 82 lung adenocarcinomas (LUAC). Twenty-nine tumors (35.4%) carried germline SNVs, and eight tumors (9.8%) harbored somatic SNVs. Interestingly, the presence of germline SNVs between positions +1 and +100 (n = 12; 14.6%) was associated with significantly shorter recurrence-free survival (RFS) and overall survival (OS) by univariate analysis (p < 0.05, respectively), and was an independent prognostic factor for RFS and OS by multivariate analysis. LUAC cell line PC9, carrying rDNA promoter SNV at position +49, showed significantly higher ribosome biogenesis than H1650 cells without SNV. Upon nucleolar stress induced by actinomycin D, PC9 retained significantly higher ribosome biogenesis than H1650. These results highlight the possible functional role of SNVs at specific sites of the rDNA promoter region in ribosome biogenesis, the progression of LUAC, and their potential prognostic value.

The p53 family reaches the final frontier: the variegated regulation of the dark matter of the genome by the p53 family in cancer

The tumour suppressor p53 and its paralogues, p63 and p73, are essential to maintain cellular homoeostasis and the integrity of the cell's genetic material, thus meriting the title of 'guardians of the genome'. The p53 family members are transcription factors and fulfill their activities by controlling the expression of protein-coding and non-coding genes. Here, we review how the latter group transcended from the 'dark matter' of the transcriptome, providing unexpected and intriguing anti-cancer therapeutic strategies.

Variant ribosomal RNA alleles are conserved and exhibit tissue-specific expression

The ribosome, the integration point for protein synthesis in the cell, is conventionally considered a homogeneous molecular assembly that only passively contributes to gene expression. Yet, epigenetic features of the ribosomal DNA (rDNA) operon and changes in the ribosome's molecular composition have been associated with disease phenotypes, suggesting that the ribosome itself may possess inherent regulatory capacity. Analyzing whole-genome sequencing data from the 1000 Genomes Project and the Mouse Genomes Project, we find that rDNA copy number varies widely across individuals, and we identify pervasive intra- and interindividual nucleotide variation in the 5S, 5.8S, 18S, and 28S ribosomal RNA (rRNA) genes of both human and mouse. Conserved rRNA sequence heterogeneities map to functional centers of the assembled ribosome, variant rRNA alleles exhibit tissue-specific expression, and ribosomes bearing variant rRNA alleles are present in the actively translating ribosome pool. These findings provide a critical framework for exploring the possibility that the expression of genomically encoded variant rRNA alleles gives rise to physically and functionally heterogeneous ribosomes that contribute to mammalian physiology and human disease.

The GALNT9, BNC1 and CCDC8 genes are frequently epigenetically dysregulated in breast tumours that metastasise to the brain

Background

Tumour metastasis to the brain is a common and deadly development in certain cancers; 18–30 % of breast tumours metastasise to the brain. The contribution that gene silencing through epigenetic mechanisms plays in these metastatic tumours is not well understood.

Results

We have carried out a bioinformatic screen of genome-wide breast tumour methylation data available at The Cancer Genome Atlas (TCGA) and a broad literature review to identify candidate genes that may contribute to breast to brain metastasis (BBM). This analysis identified 82 candidates. We investigated the methylation status of these genes using Combined Bisulfite and Restriction Analysis (CoBRA) and identified 21 genes frequently methylated in BBM. We have identified three genes, GALNT9, CCDC8 and BNC1, that were frequently methylated (55, 73 and 71 %, respectively) and silenced in BBM and infrequently methylated in primary breast tumours. CCDC8 was commonly methylated in brain metastases and their associated primary tumours whereas GALNT9 and BNC1 were methylated and silenced only in brain metastases, but not in the associated primary breast tumours from individual patients. This suggests differing roles for these genes in the evolution of metastatic tumours; CCDC8 methylation occurs at an early stage of metastatic evolution whereas methylation of GANLT9 and BNC1 occurs at a later stage of tumour evolution. Knockdown of these genes by RNAi resulted in a significant increase in the migratory and invasive potential of breast cancer cell lines.

Conclusions

These findings indicate that GALNT9 (an initiator of O-glycosylation), CCDC8 (a regulator of microtubule dynamics) and BNC1 (a transcription factor with a broad range of targets) may play a role in the progression of primary breast tumours to brain metastases. These genes may be useful as prognostic markers and their products may provide novel therapeutic targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0089-x) contains supplementary material, which is available to authorized users.

Basonuclin-1 modulates epithelial plasticity and TGF-β1-induced loss of epithelial cell integrity

Transforming growth factor-β1 (TGF-β1) is a multifunctional cytokine and critically involved in the progression of a variety of cancers. TGF-β1 signaling can impair tumor development by its anti-proliferative and pro-apoptotic features. In contrast, it may actively promote tumor progression and cancer cell dissemination by inducing a gradual switch from epithelial towards mesenchymal-like cell features (EMT-like), including decreased intercellular adhesion. Here, we show that expression of the transcription factor Basonuclin-1 (Bnc1) modulates TGF-β1-induced epithelial dedifferentiation of mammary epithelial cells. RNAi-mediated repression of Bnc1 resulted in enhanced intercellular adhesion and strongly impaired TGF-β1-dependent sheet disintegration and cell scattering. In contrast, forced expression of Bnc1 modifies plasma membrane/cytoskeletal dynamics and seemingly interferes with the initiation of sustainable cell-cell contacts. Follow-up analyses revealed that Bnc1 affects the expression of numerous TGF-β1-responsive genes including distinct EMT-related transcription factors, some of which modulate the expression of Bnc1 themselves. These results suggest that Bnc1 is part of a transcription factor network related to epithelial plasticity with reciprocal feedback-loop connections on which Smad-factors integrate TGF-β1 signaling. Our study demonstrates that Bnc1 regulates epithelial plasticity of mammary epithelial cells and influences outcome of TGF-β1 signaling.

HSF2BP represses BNC1 transcriptional activity by sequestering BNC1 to the cytoplasm

Basonuclin (BNC1), a zinc finger transcriptional factor, is essential for mouse spermatogenesis. However, the regulatory mechanisms of BNC1 in spermatogenesis are poorly understood. In this study, we identified HSF2BP, a testis-specific binding protein of HSF2, as a binding partner of BNC1 by using yeast two-hybrid screening. HSF2BP could interact with and inhibit BNC1 transcriptional activity without affecting its expression level. Moreover, coexpression of HSF2BP with BNC1 resulted in a striking redistribution of BNC1 to the cytoplasm. These data suggest that HSF2BP may play a pivotal role in regulating BNC1 transcriptional activity and subcellular localization during spermatogenesis.

Molecular and organismal changes in offspring of male mice treated with chemical stressors

Both gene methylation changes and genetic instability have been noted in offspring of male rodents exposed to radiation or chemicals, but few specific gene targets have been established. Previously, we identified the gene for ribosomal RNA, rDNA, as showing methylation change in sperm of mice treated with the preconceptional carcinogen, chromium(III) chloride. rDNA is a critical cell growth regulator. Here, we investigated the effects of paternal treatments on rDNA in offspring tissue. A total of 93 litters and 758 offspring were obtained, permitting rigorous mixed-effects models statistical analysis of the results. We show that the offspring of male mice treated with Cr(III) presented increased methylation in a promoter sequence of the rDNA gene, specifically in lung. Furthermore polymorphic variants of the multi-copy rDNA genes displayed altered frequencies indicative of structural changes, as a function of both tissue type and paternal treatments. Organismal effects also occurred: some groups of offspring of male mice treated with either Cr(III) or its vehicle, acidic saline, compared with those of untreated mice, had altered average body and liver weights and levels of serum glucose and leptin. Males treated directly with Cr(III) or acidic saline presented serum hormone changes consistent with a stress response. These results establish for the first time epigenetic and genetic instability effects in a gene of central physiological importance, in offspring of male mice exposed preconceptionally to chemicals, possibly related to a stress response in these males.

BNC1 is required for maintaining mouse spermatogenesis

Basonuclin (BNC1) is a zinc finger protein expressed primarily in gametogenic cells and proliferative keratinocytes. Our previous work suggested that BNC1 is present in spermatogonia, spermatocytes, and spermatids, but absent in the Sertoli cells. BNC1's role in spermatogenesis is unknown. Here, we show that BNC1 is required for the maintenance of spermatogenesis. Bnc1-null male mice were sub-fertile, losing germ cells progressively with age. The Bnc1-null seminiferous epithelia began to degenerate before 8 weeks of age and eventually became Sertoli cell-only. Sperm count and motility also declined with age. Furthermore, Bnc1 heterozygotes, although fertile, showed a significant drop in sperm count and in testis weight by 24 weeks of age, suggesting a dosage effect of Bnc1 on testis development. In conclusion, our data demonstrate for the first time BNC1's essential role in maintaining mouse spermatogenesis.

p63 Transcriptionally regulates BNC1, a Pol I and Pol II transcription factor that regulates ribosomal biogenesis and epithelial differentiation

The p53-family member, p63 is a transcription factor that influences cellular adhesion, motility, proliferation, survival and apoptosis, and has a major role in regulating epithelial stem cells. Expression of p63 is often dysregulated in squamous cell carcinomas of the head and neck. In this study we show that p63 induces the expression of the basal epithelial transcription factor, Basonuclin 1. Basonuclin 1 is an unusual transcription factor that interacts with a subset of promoters of genes that are transcribed by both RNA polymerase-I and -II and has roles in maintaining ribosomal biogenesis and the proliferative potential of immature epithelial cells. Chromatin immunoprecipitation and reporter assays demonstrate that Basonuclin 1 is a direct transcriptional target of p63 and we also show that up-regulation of Basonuclin 1 is a common event in squamous cell carcinomas of the head and neck. These data identify a new transcriptional programme mediated by p63 regulation of the Basonuclin 1 transcription factor in squamous cell carcinomas and provide a novel link of p63 with the regulation of ribosomal biogenesis in epithelial cancer.

Basonuclin-2 requirements for zebrafish adult pigment pattern development and female fertility

Relatively little is known about the generation of adult form. One complex adult trait that is particularly amenable to genetic and experimental analysis is the zebrafish pigment pattern, which undergoes extensive remodeling during post-embryonic development to form adult stripes. These stripes result from the arrangement of three classes of neural crest-derived pigment cells, or chromatophores: melanophores, xanthophores, and iridophores. Here, we analyze the zebrafish bonaparte mutant, which has a normal early pigment pattern but exhibits a severe disruption to the adult stripe pattern. We show that the bonaparte mutant phenotype arises from mutations in basonuclin-2 (bnc2), encoding a highly conserved, nuclear-localized zinc finger protein of unknown function. We show that bnc2 acts non-autonomously to the melanophore lineage and is expressed by hypodermal cells adjacent to chromatophores during adult pigment pattern formation. In bonaparte (bnc2) mutants, all three types of chromatophores differentiate but then are lost by extrusion through the skin. We further show that while bnc2 promotes the development of two genetically distinct populations of melanophores in the body stripes, chromatophores of the fins and scales remain unaffected in bonaparte mutants, though a requirement of fin chromatophores for bnc2 is revealed in the absence of kit and colony stimulating factor-1 receptor activity. Finally, we find that bonaparte (bnc2) mutants exhibit dysmorphic ovaries correlating with infertility and bnc2 is expressed in somatic ovarian cells, whereas the related gene, bnc1, is expressed within oocytes; and we find that both bnc2 and bnc1 are expressed abundantly within the central nervous system. These findings identify bnc2 as an important mediator of adult pigment pattern formation and identify bonaparte mutants as an animal model for dissecting bnc2 functions.

An intergenic non-coding rRNA correlated with expression of the rRNA and frequency of an rRNA single nucleotide polymorphism in lung cancer cells

BACKGROUND

Ribosomal RNA (rRNA) is a central regulator of cell growth and may control cancer development. A cis noncoding rRNA (nc-rRNA) upstream from the 45S rRNA transcription start site has recently been implicated in control of rRNA transcription in mouse fibroblasts. We investigated whether a similar nc-rRNA might be expressed in human cancer epithelial cells, and related to any genomic characteristics.

METHODOLOGY/PRINCIPAL FINDINGS

Using quantitative rRNA measurement, we demonstrated that a nc-rRNA is transcribed in human lung epithelial and lung cancer cells, starting from approximately -1000 nucleotides upstream of the rRNA transcription start site (+1) and extending at least to +203. This nc-rRNA was significantly more abundant in the majority of lung cancer cell lines, relative to a nontransformed lung epithelial cell line. Its abundance correlated negatively with total 45S rRNA in 12 of 13 cell lines (P = 0.014). During sequence analysis from -388 to +306, we observed diverse, frequent intercopy single nucleotide polymorphisms (SNPs) in rRNA, with a frequency greater than predicted by chance at 12 sites. A SNP at +139 (U/C) in the 5' leader sequence varied among the cell lines and correlated negatively with level of the nc-rRNA (P = 0.014). Modelling of the secondary structure of the rRNA 5'-leader sequence indicated a small increase in structural stability due to the +139 U/C SNP and a minor shift in local configuration occurrences.

CONCLUSIONS/SIGNIFICANCE

The results demonstrate occurrence of a sense nc-rRNA in human lung epithelial and cancer cells, and imply a role in regulation of the rRNA gene, which may be affected by a +139 SNP in the 5' leader sequence of the primary rRNA transcript.

Mouse ribosomal RNA genes contain multiple differentially regulated variants

Previous cytogenetic studies suggest that various rDNA chromosomal loci are not equally active in different cell types. Consistent with this variability, rDNA polymorphism is well documented in human and mouse. However, attempts to identify molecularly rDNA variant types, which are regulated individually (i.e., independent of other rDNA variants) and tissue-specifically, have not been successful. We report here the molecular cloning and characterization of seven mouse rDNA variants (v-rDNA). The identification of these v-rDNAs was based on restriction fragment length polymorphisms (RFLPs), which are conserved among individuals and mouse strains. The total copy number of the identified variants is less than 100 and the copy number of each individual variant ranges from 4 to 15. Sequence analysis of the cloned v-rDNA identified variant-specific single nucleotide polymorphisms (SNPs) in the transcribed region. These SNPs were used to develop a set of variant-specific PCR assays, which permitted analysis of the v-rDNAs' expression profiles in various tissues. These profiles show that three v-rDNAs are expressed in all tissues (constitutively active), two are expressed in some tissues (selectively active), and two are not expressed (silent). These expression profiles were observed in six individuals from three mouse strains, suggesting the pattern is not randomly determined. Thus, the mouse rDNA array likely consists of genetically distinct variants, and some are regulated tissue-specifically. Our results provide the first molecular evidence for cell-type-specific regulation of a subset of rDNA.

Nucleolus: the fascinating nuclear body

Nucleoli are the prominent contrasted structures of the cell nucleus. In the nucleolus, ribosomal RNAs are synthesized, processed and assembled with ribosomal proteins. RNA polymerase I synthesizes the ribosomal RNAs and this activity is cell cycle regulated. The nucleolus reveals the functional organization of the nucleus in which the compartmentation of the different steps of ribosome biogenesis is observed whereas the nucleolar machineries are in permanent exchange with the nucleoplasm and other nuclear bodies. After mitosis, nucleolar assembly is a time and space regulated process controlled by the cell cycle. In addition, by generating a large volume in the nucleus with apparently no RNA polymerase II activity, the nucleolus creates a domain of retention/sequestration of molecules normally active outside the nucleolus. Viruses interact with the nucleolus and recruit nucleolar proteins to facilitate virus replication. The nucleolus is also a sensor of stress due to the redistribution of the ribosomal proteins in the nucleoplasm by nucleolus disruption. The nucleolus plays several crucial functions in the nucleus: in addition to its function as ribosome factory of the cells it is a multifunctional nuclear domain, and nucleolar activity is linked with several pathologies. Perspectives on the evolution of this research area are proposed.

Basonuclin-null mutation impairs homeostasis and wound repair in mouse corneal epithelium

At least two cellular processes are required for corneal epithelium homeostasis and wound repair: cell proliferation and cell-cell adhesion. These processes are delicately balanced to ensure the maintenance of normal epithelial function. During wound healing, these processes must be reprogrammed in coordination to achieve a rapid re-epithelialization. Basonuclin (Bnc1) is a cell-type-specific transcription factor expressed mainly in the proliferative keratinocytes of stratified epithelium (e.g., corneal epithelium, epidermis and esophageal epithelium) and the gametogenic cells in testis and ovary. Our previous work suggested that basonuclin could regulate transcription of ribosomal RNA genes (rDNA) and genes involved in chromatin structure, transcription regulation, cell-cell junction/communication, ion-channels and intracelllular transportation. However, basonuclin's role in keratinocytes has not been demonstrated in vivo. Here we show that basonuclin-null mutation disrupts corneal epithelium homeostasis and delays wound healing by impairing cell proliferation. In basonuclin-null cornea epithelium, RNA polymerase I (Pol I) transcription is perturbed. This perturbation is unique because it affects transcripts from a subset of rDNA. Basonuclin-null mutation also perturbs RNA polymerase II (Pol II) transcripts from genes encoding chromatin structure proteins histone 3 and HMG2, transcription factor Gli2, gap-junction protein connexin 43 and adheren E-cadherin. In most cases, a concerted change in mRNA and protein level is observed. However, for E-cadherin, despite a notable increase in its mRNA level, its protein level was reduced. In conclusion, our study establishes basonuclin as a regulator of corneal epithelium homeostasis and maintenance. Basonuclin likely coordinates functions of a subset of ribosomal RNA genes (rDNA) and a group of protein coding genes in cellular processes critical for the regulation of cell proliferation.