Functional coupling of transcription factor HiNF-P and histone H4 gene expression during pre- and post-natal mouse development

Downregulation of HINFP induces senescence-associated secretory phenotype to promote metastasis in a non-cell-autonomous manner in bladder cancer

Transcription dysregulation is a salient characteristic of bladder cancer (BC), but no appropriate therapeutic target for it has been established. Here, we found that heterogeneous downregulation of histone H4 transcription factor (HINFP) was associated with senescence in BC tissues and that lower HINFP expression could predict an unfavorable outcome in BC patients. Knockout of HINFP transcriptionally inhibited H1F0 and H1FX to trigger DNA damage, consequently inducing cell senescence to repress the proliferation and growth of BC cells. However, the senescence-associated secretory phenotype, characterized by increases in MMP1/3, enhances the invasion and metastasis of non-senescent BC cells. Histone deacetylase inhibitors (HDACis) could efficiently eliminate the senescent cells induced by HINFP knockout to suppress the invasion and metastasis of BC cells. Our study suggests that HDACis, widely used in multiple cancer types in a clinical context, may also benefit BC patients with metastases induced by cell senescence.

Loss of a Newly Discovered microRNA in Chinese Hamster Ovary Cells Leads to Upregulation of NGNA Sialylation on Monoclonal Antibodies

Chinese hamster ovary (CHO) cells are known not to express appreciable levels of the sialic acid residue N‐glycolylneuraminic acid (NGNA) on monoclonal antibodies. However, we actually have identified a recombinant CHO cell line expressing an IgG with unusually high levels of NGNA sialylation (>30%). Comprehensive multi‐OMICs based experimental analyses unraveled the root cause of this atypical sialylation: (1) expression of the cytidine monophosphate‐N‐acetylneuraminic acid hydroxylase (CMAH) gene was spontaneously switched on, (2) CMAH mRNA showed an anti‐correlated expression to the newly discovered Cricetulus griseus (cgr) specific microRNA cgr‐miR‐111 and exhibits two putative miR‐111 binding sites, (3) miR‐111 expression depends on the transcription of its host gene SDK1, and (4) a single point mutation within the promoter region of the sidekick cell adhesion molecule 1 (SDK1) gene generated a binding site for the transcriptional repressor histone H4 transcription factor HINF‐P. The resulting transcriptional repression of SDK1 led to a downregulation of its co‐expressed miR‐111 and hence to a spontaneous upregulation of CMAH expression finally increasing NGNA protein sialylation.

Hinfp is a guardian of the somatic genome by repressing transposable elements

Germ cells possess the Piwi-interacting RNA pathway to repress transposable elements and maintain genome stability across generations. Transposable element mobilization in somatic cells does not affect future generations, but nonetheless can lead to pathological outcomes in host tissues. We show here that loss of function of the conserved zinc-finger transcription factor Hinfp causes dysregulation of many host genes and derepression of most transposable elements. There is also substantial DNA damage in somatic tissues of Drosophila after loss of Hinfp. Interference of transposable element mobilization by reverse-transcriptase inhibitors can suppress some of the DNA damage phenotypes. The key cell-autonomous target of Hinfp in this process is Histone1, which encodes linker histones essential for higher-order chromatin assembly. Transgenic expression of Hinfp or Histone1, but not Histone4 of core nucleosome, is sufficient to rescue the defects in repressing transposable elements and host genes. Loss of Hinfp enhances Ras-induced tissue growth and aging-related phenotypes. Therefore, Hinfp is a physiological regulator of Histone1-dependent silencing of most transposable elements, as well as many host genes, and serves as a venue for studying genome instability, cancer progression, neurodegeneration, and aging.

Transcriptional Regulation by CpG Sites Methylation in the Core Promoter Region of the Bovine SIX1 Gene: Roles of Histone H4 and E2F2

DNA methylation is a major epigenetic modification of the genome and has an essential role in muscle development. The SIX1 gene is thought to play a principal role in mediating skeletal muscle development. In the present study, we determined that bovine SIX1 expression levels were significantly higher in the fetal bovine group (FB) and in undifferentiated Qinchuan cattle muscle cells (QCMCs) than in the adult bovine group (AB) and in differentiated QCMCs. Moreover, a bisulfite sequencing polymerase chain reaction (BSP) analysis of DNA methylation levels showed that three CpG sites in the core promoter region (−216/−28) of the bovine SIX1 gene exhibited significantly higher DNA methylation levels in the AB and differentiated QCMCs groups. In addition, we found that DNA methylation of SIX1 core promoter in vitro obviously influences the promoter activities. An electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay, in combination with site-directed mutation and siRNA interference, demonstrated that histone H4 and E2F2 bind to the −216/−28 region and play important roles in SIX1 methylation regulation during development. The results of this study provide the foundation for a better understanding of the regulation of bovine SIX1 expression via methylation and muscle developmental in beef cattle.

Maternal expression and early induction of histone gene transcription factor Hinfp sustains development in pre-implantation embryos

Fidelity of histone gene expression is important for normal cell growth and differentiation that is stringently controlled during development but is compromised during tumorigenesis. Efficient production of histones for packaging newly replicated DNA is particularly important for proper cell division and epigenetic control during the initial pre-implantation stages of embryonic development. Here, we addressed the unresolved question of when the machinery for histone gene transcription is activated in the developing zygote to accommodate temporal demands for histone gene expression. We examined induction of Histone Nuclear Factor P (HINFP), the only known transcription factor required for histone H4 gene expression, that binds directly to a unique H4 promoter-specific element to regulate histone H4 transcription. We show that Hinfp gene transcripts are stored in oocytes and maternally transmitted to the zygote. Transcripts from the paternal Hinfp gene, which reflect induction of zygotic gene expression, are apparent at the 4- to 8-cell stage, when most maternal mRNA pools are depleted. Loss of Hinfp expression due to gene ablation reduces cell numbers in E3.5 stage embryos and compromises implantation. Reduced cell proliferation is attributable to severe reduction in histone mRNA levels accompanied by reduced cell survival and genomic damage as measured by cleaved Caspase 3 and phospho-H2AX staining, respectively. We conclude that transmission of maternal Hinfp transcripts and zygotic activation of the Hinfp gene together are necessary to control H4 gene expression in early pre-implantation embryos in order to support normal embryonic development.

Cell cycle gene expression networks discovered using systems biology: Significance in carcinogenesis

The early stages of carcinogenesis are linked to defects in the cell cycle. A series of cell cycle checkpoints are involved in this process. The G1/S checkpoint that serves to integrate the control of cell proliferation and differentiation is linked to carcinogenesis and the mitotic spindle checkpoint is associated with the development of chromosomal instability. This paper presents the outcome of systems biology studies designed to evaluate if networks of covariate cell cycle gene transcripts exist in proliferative mammalian tissues including mice, rats, and humans. The GeneNetwork website that contains numerous gene expression datasets from different species, sexes, and tissues represents the foundational resource for these studies (www.genenetwork.org). In addition, WebGestalt, a gene ontology tool, facilitated the identification of expression networks of genes that co-vary with key cell cycle targets, especially Cdc20 and Plk1 (www.bioinfo.vanderbilt.edu/webgestalt). Cell cycle expression networks of such covariate mRNAs exist in multiple proliferative tissues including liver, lung, pituitary, adipose, and lymphoid tissues among others but not in brain or retina that have low proliferative potential. Sixty-three covariate cell cycle gene transcripts (mRNAs) compose the average cell cycle network with P = e(-13) to e(-36) . Cell cycle expression networks show species, sex and tissue variability, and they are enriched in mRNA transcripts associated with mitosis, many of which are associated with chromosomal instability.

p53 checkpoint ablation exacerbates the phenotype of Hinfp dependent histone H4 deficiency

Histone Nuclear Factor P (HINFP) is essential for expression of histone H4 genes. Ablation of Hinfp and consequential depletion of histones alter nucleosome spacing and cause stalled replication and DNA damage that ultimately result in genomic instability. Faithful replication and packaging of newly replicated DNA are required for normal cell cycle control and proliferation. The tumor suppressor protein p53, the guardian of the genome, controls multiple cell cycle checkpoints and its loss leads to cellular transformation. Here we addressed whether the absence of p53 impacts the outcomes/consequences of Hinfp-mediated histone H4 deficiency. We examined mouse embryonic fibroblasts lacking both Hinfp and p53. Our data revealed that the reduced histone H4 expression caused by depletion of Hinfp persists when p53 is also inactivated. Loss of p53 enhanced the abnormalities in nuclear shape and size (i.e. multi-lobed irregularly shaped nuclei) caused by Hinfp depletion and also altered the sub-nuclear organization of Histone Locus Bodies (HLBs). In addition to the polyploid phenotype resulting from deletion of either p53 or Hinfp, inactivation of both p53 and Hinfp increased mitotic defects and generated chromosomal fragility and susceptibility to DNA damage. Thus, our study conclusively establishes that simultaneous loss of both Hinfp and the p53 checkpoint is detrimental to normal cell growth and may predispose to cellular transformation.

A screen of zebrafish mutants identifies ethanol-sensitive genetic loci

BACKGROUND

Fetal alcohol spectrum disorders (FASD) are a highly variable set of phenotypes caused by fetal alcohol exposure. Numerous factors influence FASD phenotypes, including genetics. The zebrafish is a powerful vertebrate model system with which to identify these genetic factors. Many zebrafish mutants are housed at the Zebrafish International Resource Center (ZIRC). These mutants are readily accessible and an excellent source to screen for ethanol (EtOH)-sensitive developmental structural mutants.

METHODS

We screened mutants obtained from ZIRC for sensitivity to EtOH teratogenesis. Embryos were treated with 1% EtOH (41 mM tissue levels) from 6 hours postfertilization onward. Levels of apoptosis were evaluated at 24 hours postfertilization. At 4 days postfertilization, the craniofacial skeleton, peripheral axon projections, and sensory neurons of neuromasts were examined. Fish were genotyped to determine whether there were phenotype/genotype correlations.

RESULTS

Five of 20 loci interacted with EtOH. Notable among these was that vangl2, involved in convergent extension movements of the embryonic axis, interacted strongly with EtOH. Untreated vangl2 mutants had normal craniofacial morphology, while severe midfacial defects including synophthalmia and narrowing of the palatal skeleton were found in all EtOH-treated mutants and a low percentage of heterozygotes. The cell cycle gene, plk1, also interacted strongly with EtOH. Untreated mutants have slightly elevated levels of apoptosis and loss of ventral craniofacial elements. Exposure to EtOH results in extensive apoptosis along with loss of neural tissue and the entire craniofacial skeleton. Phenotypes of hinfp, mars, and foxi1 mutants were also exacerbated by EtOH.

CONCLUSIONS

Our results provide insight into the gene-EtOH interactions that may underlie EtOH teratogenesis. They support previous findings that EtOH disrupts elongation of the embryonic axis. Importantly, these results show that the zebrafish is an efficient model with which to test for gene-EtOH interactions. Understanding these interactions will be crucial to understanding of the FASD variation.