Transcription factor EGR2 controls homing and pathogenicity of TH17 cells in the central nervous system.

CD4+ T helper 17 (TH17) cells protect barrier tissues but also trigger autoimmunity. The mechanisms behind these opposing processes remain unclear. Here, we found that the transcription factor EGR2 controlled the transcriptional program of pathogenic TH17 cells in the central nervous system (CNS) but not that of protective TH17 cells at barrier sites. EGR2 was significantly elevated in myelin-reactive CD4+ T cells from patients with multiple sclerosis and mice with autoimmune neuroinflammation. The EGR2 transcriptional program was intricately woven within the TH17 cell transcriptional regulatory network and showed high interconnectivity with core TH17 cell-specific transcription factors. Mechanistically, EGR2 enhanced TH17 cell differentiation and myeloid cell recruitment to the CNS by upregulating pathogenesis-associated genes and myelomonocytic chemokines. T cell-specific deletion of Egr2 attenuated neuroinflammation without compromising the host's ability to control infections. Our study shows that EGR2 regulates tissue-specific and disease-specific functions in pathogenic TH17 cells in the CNS.

DNAJC9 prevents CENP-A mislocalization and chromosomal instability by maintaining the fidelity of histone supply chains.

The centromeric histone H3 variant CENP-A is overexpressed in many cancers. The mislocalization of CENP-A to noncentromeric regions contributes to chromosomal instability (CIN), a hallmark of cancer. However, pathways that promote or prevent CENP-A mislocalization remain poorly defined. Here, we performed a genome-wide RNAi screen for regulators of CENP-A localization which identified DNAJC9, a J-domain protein implicated in histone H3-H4 protein folding, as a factor restricting CENP-A mislocalization. Cells lacking DNAJC9 exhibit mislocalization of CENP-A throughout the genome, and CIN phenotypes. Global interactome analysis showed that DNAJC9 depletion promotes the interaction of CENP-A with the DNA-replication-associated histone chaperone MCM2. CENP-A mislocalization upon DNAJC9 depletion was dependent on MCM2, defining MCM2 as a driver of CENP-A deposition at ectopic sites when H3-H4 supply chains are disrupted. Cells depleted for histone H3.3, also exhibit CENP-A mislocalization. In summary, we have defined novel factors that prevent mislocalization of CENP-A, and demonstrated that the integrity of H3-H4 supply chains regulated by histone chaperones such as DNAJC9 restrict CENP-A mislocalization and CIN.

Interferon induced circRNAs escape herpesvirus host shutoff and suppress lytic infection.

To globally profile circRNAs, we employ RNA-Sequencing paired with chimeric junction analysis for alpha-, beta-, and gamma-herpesvirus infection. We find circRNAs are, as a population, resistant to host shutoff. We validate this observation using ectopic expression assays of human and murine herpesvirus endoribonucleases. During lytic infection, four circRNAs are commonly induced across all subfamilies of human herpesviruses, suggesting a shared mechanism of regulation. We test one such mechanism, namely how interferon-stimulation influences circRNA expression. 67 circRNAs are upregulated by either interferon-ß or -γ treatment, with half of these also upregulated during lytic infection. Using gain and loss of function studies we find an interferon-stimulated circRNA, circRELL1, inhibits lytic Herpes Simplex Virus-1 infection. We previously reported circRELL1 inhibits lytic Kaposi sarcoma-associated herpesvirus infection, suggesting a pan-herpesvirus antiviral activity. We propose a two-pronged model in which interferon-stimulated genes may encode both mRNA and circRNA with antiviral activity. This is critical in cases of host shutoff, such as alpha- and gamma-herpesvirus infection, where the mRNA products are degraded but circRNAs escape.

A virus-induced circular RNA maintains latent infection of Kaposi's sarcoma herpesvirus.

Non-coding RNAs (ncRNAs) play important roles in host-pathogen interactions; oncogenic viruses like Kaposi's sarcoma herpesvirus (KSHV) employ ncRNAs to establish a latent reservoir and persist for the life of the host. We previously reported that KSHV infection alters a novel class of RNA, circular RNAs (circRNAs). CircRNAs are alternative splicing isoforms and regulate gene expression, but their importance in infection is largely unknown. Here, we showed that a human circRNA, hsa_circ_0001400, is induced by various pathogenic viruses, namely KSHV, Epstein-Barr virus, and human cytomegalovirus. The induction of circRNAs including circ_0001400 by KSHV is co-transcriptionally regulated, likely at splicing. Consistently, screening for circ_0001400-interacting proteins identified a splicing factor, PNISR. Functional studies using infected primary endothelial cells revealed that circ_0001400 inhibits KSHV lytic transcription and virus production. Simultaneously, the circRNA promoted cell cycle, inhibited apoptosis, and induced immune genes. RNA-pull down assays identified transcripts interacting with circ_0001400, including TTI1, which is a component of the pro-growth mTOR complexes. We thus identified a circRNA that is pro-growth and anti-lytic replication. These results support a model in which KSHV induces circ_0001400 expression to maintain latency. Since circ_0001400 is induced by multiple viruses, this novel viral strategy may be widely employed by other viruses.

Transcriptional landscape of Kaposi sarcoma tumors identifies unique immunologic signatures and key determinants of angiogenesis.

BACKGROUND: Kaposi sarcoma (KS) is a multicentric tumor caused by Kaposi sarcoma herpesvirus (KSHV) that leads to morbidity and mortality among people with HIV worldwide. KS commonly involves the skin but can occur in the gastrointestinal tract (GI) in severe cases. METHODS: RNA sequencing was used to compare the cellular and KSHV gene expression signatures of skin and GI KS lesions in 44 paired samples from 19 participants with KS alone or with concurrent KSHV-associated diseases. Analyses of KSHV expression from KS lesions identified transcriptionally active areas of the viral genome. RESULTS: The transcript of an essential viral lytic gene, ORF75, was detected in 91% of KS lesions. Analyses of host genes identified 370 differentially expressed genes (DEGs) unique to skin KS and 58 DEGs unique to GI KS lesions as compared to normal tissue. Interleukin (IL)-6 and IL-10 gene expression were higher in skin lesions as compared to normal skin but not in GI KS lesions. Twenty-six cellular genes were differentially expressed in both skin and GI KS tissues: these included Fms-related tyrosine kinase 4 (FLT4), encoding an angiogenic receptor, and Stanniocalcin 1 (STC1), a secreted glycoprotein. FLT4 and STC1 were further investigated in functional studies using primary lymphatic endothelial cells (LECs). In these models, KSHV infection of LECs led to increased tubule formation that was impaired upon knock-down of STC1 or FLT4. CONCLUSIONS: This study of transcriptional profiling of KS tissue provides novel insights into the characteristics and pathogenesis of this unique virus-driven neoplasm.

Ubiquitination of MHC Class II by March-I Regulates Dendritic Cell Fitness.

The expression and turnover of Ag-specific peptide-MHC class II (pMHC-II) on the surface of dendritic cells (DCs) is essential for their ability to efficiently activate CD4 T cells. Ubiquitination of pMHC-II by the E3 ubiquitin ligase March-I regulates surface expression and survival of pMHC-II in DCs. We now show that despite their high levels of surface pMHC-II, MHC class II (MHC-II) ubiquitination-deficient mouse DCs are functionally defective; they are poor stimulators of naive CD4 T cells and secrete IL-12 in response to LPS stimulation poorly. MHC-II ubiquitination-mutant DC defects are cell intrinsic, and single-cell RNA sequencing demonstrates that these DCs have an altered gene expression signature as compared with wild-type DCs. Curiously, these functional and gene transcription defects are reversed by activating the DCs with LPS. These results show that dysregulation of MHC-II turnover suppresses DC development and function.

Identifying and characterizing virus-encoded circular RNAs.

Circular forms of RNA were first discovered in plant viroids and later found in a variety of animal viruses. These circular RNAs lack free 5' and 3' ends, granting protection from exonucleases. This review is focused on the methods that are used to investigate virus-encoded circular RNAs. Using DNA viruses that are prevalent among human as examples, we begin with features of circular RNAs and the unique methods to enrich for circular RNAs. Next, we discuss the computational methods for RNA-sequencing analysis to discover new virus-encoded circular RNAs. Many strategies are similar to analyzing cellular RNAs, but some unique aspects of virus-encoded circular RNAs that are likely due to highly packed viral genomes and non-canonical use of splicing machinery, are described herein. We illustrate the various methods of validating expression of specific virus-encoded circular RNAs. Finally, we discuss novel methods to study functions of circular RNAs and the current technical challenges that remain for investigating virus-encoded circular RNAs.

Discovery of Kaposi's sarcoma herpesvirus-encoded circular RNAs and a human antiviral circular RNA.

Noncoding RNAs have substantial effects in host-virus interactions. Circular RNAs (circRNAs) are novel single-stranded noncoding RNAs which can decoy other RNAs or RNA-binding proteins to inhibit their functions. The role of circRNAs is largely unknown in the context of Kaposi's sarcoma herpesvirus (KSHV). We hypothesized that circRNAs influence viral infection by inhibiting host and/or viral factors. Transcriptome analysis of KSHV-infected primary endothelial cells and a B cell line identified human circRNAs that are differentially regulated upon infection. We confirmed the expression changes with divergent PCR primers and RNase R treatment of specific circRNAs. Ectopic expression of hsa_circ_0001400, a circRNA induced by infection, suppressed expression of key viral latent gene LANA and lytic gene RTA in KSHV de novo infections. Since human herpesviruses express noncoding RNAs like microRNAs, we searched for viral circRNAs encoded in the KSHV genome. We performed circRNA-Seq analysis with RNase R-treated, circRNA-enriched RNA from KSHV-infected cells. We identified multiple circRNAs encoded by the KSHV genome that are expressed in KSHV-infected endothelial cells and primary effusion lymphoma (PEL) cells. The KSHV circRNAs are located within ORFs of viral lytic genes, are up-regulated upon the induction of the lytic cycle, and alter cell growth. Viral circRNAs were also detected in lymph nodes from patients of KSHV-driven diseases such as PEL, Kaposi's sarcoma, and multicentric Castleman's disease. We revealed new host-virus interactions of circRNAs: human antiviral circRNAs are activated in response to KSHV infection, and viral circRNA expression is induced in the lytic phase of infection.

Loss of myeloid-specific lamin A/C drives lung metastasis through Gfi-1 and C/EBPε-mediated granulocytic differentiation.

The immune-suppressive tumor microenvironment promotes metastatic spread and outgrowth. One of the major contributors is tumor-associated myeloid cells. However, the molecular mechanisms regulating their differentiation and function are not well understood. Here we report lamin A/C, a nuclear lamina protein associated with chromatin remodeling, was one of the critical regulators in cellular reprogramming of tumor-associated myeloid cells. Using myeloid-specific lamin A/C knockout mice and triple-negative breast cancer (TNBC) mouse models, we discovered that the loss of lamin A/C drives CD11b+ Ly6G+ granulocytic lineage differentiation, alters the production of inflammatory chemokines, decreases host antitumor immunity, and increases metastasis. The underlying mechanisms involve an increased H3K4me3 leading to the upregulation of transcription factors (TFs) Gfi-1 and C/EBPε. Decreased lamin A/C and increased Gfi-1 and C/EBPε were also found in the granulocytic subset in the peripheral blood of human cancer patients. Our data provide a mechanistic understanding of myeloid lineage differentiation and function in the immune-suppressive microenvironment in TNBC metastasis.

Genomic comparison of Trypanosoma conorhini and Trypanosoma rangeli to Trypanosoma cruzi strains of high and low virulence.

BACKGROUND: Trypanosoma conorhini and Trypanosoma rangeli, like Trypanosoma cruzi, are kinetoplastid protist parasites of mammals displaying divergent hosts, geographic ranges and lifestyles. Largely nonpathogenic T. rangeli and T. conorhini represent clades that are phylogenetically closely related to the T. cruzi and T. cruzi-like taxa and provide insights into the evolution of pathogenicity in those parasites. T. rangeli, like T. cruzi is endemic in many Latin American countries, whereas T. conorhini is tropicopolitan. T. rangeli and T. conorhini are exclusively extracellular, while T. cruzi has an intracellular stage in the mammalian host. RESULTS: Here we provide the first comprehensive sequence analysis of T. rangeli AM80 and T. conorhini 025E, and provide a comparison of their genomes to those of T. cruzi G and T. cruzi CL, respectively members of T. cruzi lineages TcI and TcVI. We report de novo assembled genome sequences of the low-virulent T. cruzi G, T. rangeli AM80, and T. conorhini 025E ranging from ~ 21-25 Mbp, with ~ 10,000 to 13,000 genes, and for the highly virulent and hybrid T. cruzi CL we present a ~ 65 Mbp in-house assembled haplotyped genome with ~ 12,500 genes per haplotype. Single copy orthologs of the two T. cruzi strains exhibited ~ 97% amino acid identity, and ~ 78% identity to proteins of T. rangeli or T. conorhini. Proteins of the latter two organisms exhibited ~ 84% identity. T. cruzi CL exhibited the highest heterozygosity. T. rangeli and T. conorhini displayed greater metabolic capabilities for utilization of complex carbohydrates, and contained fewer retrotransposons and multigene family copies, i.e. trans-sialidases, mucins, DGF-1, and MASP, compared to T. cruzi. CONCLUSIONS: Our analyses of the T. rangeli and T. conorhini genomes closely reflected their phylogenetic proximity to the T. cruzi clade, and were largely consistent with their divergent life cycles. Our results provide a greater context for understanding the life cycles, host range expansion, immunity evasion, and pathogenesis of these trypanosomatids.

MeFiT: merging and filtering tool for illumina paired-end reads for 16S rRNA amplicon sequencing.

BACKGROUND: Recent advances in next-generation sequencing have revolutionized genomic research. 16S rRNA amplicon sequencing using paired-end sequencing on the MiSeq platform from Illumina, Inc., is being used to characterize the composition and dynamics of extremely complex/diverse microbial communities. For this analysis on the Illumina platform, merging and quality filtering of paired-end reads are essential first steps in data analysis to ensure the accuracy and reliability of downstream analysis. RESULTS: We have developed the Merging and Filtering Tool (MeFiT) to combine these pre-processing steps into one simple, intuitive pipeline. MeFiT invokes CASPER (context-aware scheme for paired-end reads) for merging paired-end reads and provides users the option to quality filter the reads using the traditional average Q-score metric or using a maximum expected error cut-off threshold. CONCLUSIONS: MeFiT provides an open-source solution that permits users to merge and filter paired end illumina reads. The tool has been implemented in python and the source-code is freely available at https://github.com/nisheth/MeFiT .

Dynamical System Modeling to Simulate Donor T Cell Response to Whole Exome Sequencing-Derived Recipient Peptides Demonstrates Different Alloreactivity Potential in HLA-Matched and -Mismatched Donor-Recipient Pairs.

Immune reconstitution kinetics and subsequent clinical outcomes in HLA-matched recipients of allogeneic stem cell transplantation (SCT) are variable and difficult to predict. Considering SCT as a dynamical system may allow sequence differences across the exomes of the transplant donors and recipients to be used to simulate an alloreactive T cell response, which may allow better clinical outcome prediction. To accomplish this, whole exome sequencing was performed on 34 HLA-matched SCT donor-recipient pairs (DRPs) and the nucleotide sequence differences translated to peptides. The binding affinity of the peptides to the relevant HLA in each DRP was determined. The resulting array of peptide-HLA binding affinity values in each patient was considered as an operator modifying a hypothetical T cell repertoire vector, in which each T cell clone proliferates in accordance with the logistic equation of growth. Using an iterating system of matrices, each simulated T cell clone's growth was calculated with the steady-state population being proportional to the magnitude of the binding affinity of the driving HLA-peptide complex. Incorporating competition between T cell clones responding to different HLA-peptide complexes reproduces a number of features of clinically observed T cell clonal repertoire in the simulated repertoire, including sigmoidal growth kinetics of individual T cell clones and overall repertoire, Power Law clonal frequency distribution, increase in repertoire complexity over time with increasing clonal diversity, and alteration of clonal dominance when a different antigen array is encountered, such as in SCT. The simulated, alloreactive T cell repertoire was markedly different in HLA-matched DRPs. The patterns were differentiated by rate of growth and steady-state magnitude of the simulated T cell repertoire and demonstrate a possible correlation with survival. In conclusion, exome wide sequence differences in DRPs may allow simulation of donor alloreactive T cell response to recipient antigens and may provide a quantitative basis for refining donor selection and titration of immunosuppression after SCT.

Comparison of Lactobacillus crispatus isolates from Lactobacillus-dominated vaginal microbiomes with isolates from microbiomes containing bacterial vaginosis-associated bacteria.

Vaginal lactobacilli can inhibit colonization by and growth of other bacteria, thereby preventing development of bacterial vaginosis (BV). Amongst the lactobacilli, Lactobacillus crispatus appears to be particularly effective at inhibiting growth of BV-associated bacteria. Nonetheless, some women who are colonized with this species can still develop clinical BV. Therefore, we sought to determine whether strains of L. crispatus that colonize women with lactobacilli-dominated vaginal microbiomes are distinct from strains that colonize women who develop BV. The genomes of L. crispatus isolates from four women with lactobacilli-dominated vaginal microbiomes ( <1% 16S rRNA reads above threshold from genera other than Lactobacillus) and four women with microbiomes containing BV-associated bacteria (>12% 16S rRNA reads from bacterial taxa associated with BV) were sequenced and compared. Lactic acid production by the different strains was quantified. Phage induction in the strains was also analysed. There was considerable genetic diversity between strains, and several genes were exclusive to either the strains from Lactobacillus-dominated microbiomes or those containing BV-associated bacteria. Overall, strains from microbiomes dominated by lactobacilli did not differ from strains from microbiomes containing BV-associated bacteria with respect to lactic acid production. All of the strains contained multiple phage, but there was no clear distinction between the presence or absence of BV-associated bacteria with respect to phage-induced lysis. Genes found to be exclusive to the Lactobacillus-dominated versus BV-associated bacteria-containing microbiomes could play a role in the maintenance of vaginal health and the development of BV, respectively.

3d interaction homology: The structurally known rotamers of tyrosine derive from a surprisingly limited set of information-rich hydropathic interaction environments described by maps.

Sidechain rotamer libraries are obtained through exhaustive statistical analysis of existing crystallographic structures of proteins and have been applied in multiple aspects of structural biology, for example, crystallography of relatively low-resolution structures, in homology model building and in biomolecular NMR. Little is known, however, about the driving forces that lead to the preference or suitability of one rotamer over another. Construction of 3D hydropathic interaction maps for nearly 30,000 tyrosines reveals the environment around each, in terms of hydrophobic (π-π stacking, etc.) and polar (hydrogen bonding, etc.) interactions. After partitioning the tyrosines into backbone-dependent (ϕ, ψ) bins, a map similarity metric based on the correlation coefficient was applied to each map-map pair to build matrices suitable for clustering with k-means. The first bin (-200° ≤ ϕ < -155°; -205° ≤ ψ < -160°), representing 631 tyrosines, reduced to 14 unique hydropathic environments, with most diversity arising from favorable hydrophobic interactions with many different residue partner types. Polar interactions for tyrosine include surprisingly ubiquitous hydrogen bonding with the phenolic OH and a handful of unique environments surrounding the tyrosine backbone. The memberships of all but one of the 14 environments are dominated (>50%) by a single χ(1)/χ(2) rotamer. The last environment has weak or no interactions with the tyrosine ring and its χ(1)/χ(2) rotamer is indeterminate, which is consistent with it being composed of mostly surface residues. Each tyrosine residue attempts to fulfill its hydropathic valence and thus, structural water molecules are seen in a variety of roles throughout protein structure.

Identification of a gene in Mycoplasma hominis associated with preterm birth and microbial burden in intraamniotic infection.

OBJECTIVE: Microbial invasion of the amniotic cavity is associated with spontaneous preterm labor and adverse pregnancy outcome, and Mycoplasma hominis often is present. However, the pathogenic process by which M hominis invades the amniotic cavity and gestational tissues, often resulting in chorioamnionitis and preterm birth, remains unknown. We hypothesized that strains of M hominis vary genetically with regards to their potential to invade and colonize the amniotic cavity and placenta. STUDY DESIGN: We sequenced the entire genomes of 2 amniotic fluid isolates and a placental isolate of M hominis from pregnancies that resulted in preterm births and compared them with the previously sequenced genome of the type strain PG21. We identified genes that were specific to the amniotic fluid/placental isolates. We then determined the microbial burden and the presence of these genes in another set of subjects from whom samples of amniotic fluid had been collected and were positive for M hominis. RESULTS: We identified 2 genes that encode surface-located membrane proteins (Lmp1 and Lmp-like) in the sequenced amniotic fluid/placental isolates that were truncated severely in PG21. We also identified, for the first time, a microbial gene of unknown function that is referred to in this study as gene of interest C that was associated significantly with bacterial burden in amniotic fluid and the risk of preterm delivery in patients with preterm labor. CONCLUSION: A gene in M hominis was identified that is associated significantly with colonization and/or infection of the upper reproductive tract during pregnancy and with preterm birth.

Whole exome sequencing to estimate alloreactivity potential between donors and recipients in stem cell transplantation.

Whole exome sequencing (WES) was performed on stem cell transplant donor-recipient (D-R) pairs to determine the extent of potential antigenic variation at a molecular level. In a small cohort of D-R pairs, a high frequency of sequence variation was observed between the donor and recipient exomes independent of human leucocyte antigen (HLA) matching. Nonsynonymous, nonconservative single nucleotide polymorphisms were approximately twice as frequent in HLA-matched unrelated, compared with related D-R pairs. When mapped to individual chromosomes, these polymorphic nucleotides were uniformly distributed across the entire exome. In conclusion, WES reveals extensive nucleotide sequence variation in the exomes of HLA-matched donors and recipients.

Loss of tumor suppressors promotes inflammatory tumor microenvironment and enhances LAG3+T cell mediated immune suppression.

Low response rate, treatment relapse, and resistance remain key challenges for cancer treatment with immune checkpoint blockade (ICB). Here we report that loss of specific tumor suppressors (TS) induces an inflammatory response and promotes an immune suppressive tumor microenvironment. Importantly, low expression of these TSs is associated with a higher expression of immune checkpoint inhibitory mediators. Here we identify, by using in vivo CRISPR/Cas9 based loss-of-function screening, that NF1, TSC1, and TGF-ß RII as TSs regulating immune composition. Loss of each of these three TSs leads to alterations in chromatin accessibility and enhances IL6-JAK3-STAT3/6 inflammatory pathways. This results in an immune suppressive landscape, characterized by increased numbers of LAG3+ CD8 and CD4 T cells. ICB targeting LAG3 and PD-L1 simultaneously inhibits metastatic progression in preclinical triple negative breast cancer (TNBC) mouse models of NF1-, TSC1- or TGF-ß RII- deficient tumors. Our study thus reveals a role of TSs in regulating metastasis via non-cell-autonomous modulation of the immune compartment and provides proof-of-principle for ICB targeting LAG3 for patients with NF1-, TSC1- or TGF-ß RII-inactivated cancers.

Transfer RNA acetylation regulates in vivo mammalian stress signaling.

Transfer RNA (tRNA) modifications are crucial for protein synthesis, but their position-specific physiological roles remain poorly understood. Here we investigate the impact of N4-acetylcytidine (ac4C), a highly conserved tRNA modification, using a Thumpd1 knockout mouse model. We find that loss of Thumpd1-dependent tRNA acetylation leads to reduced levels of tRNALeu, increased ribosome stalling, and activation of eIF2α phosphorylation. Thumpd1 knockout mice exhibit growth defects and sterility. Remarkably, concurrent knockout of Thumpd1 and the stress-sensing kinase Gcn2 causes penetrant postnatal lethality, indicating a critical genetic interaction. Our findings demonstrate that a modification restricted to a single position within type II cytosolic tRNAs can regulate ribosome-mediated stress signaling in mammalian organisms, with implications for our understanding of translation control as well as therapeutic interventions.

Interferon induced circRNAs escape herpesvirus host shutoff and suppress lytic infection.

A first line of defense during infection is expression of interferon (IFN)-stimulated gene products which suppress viral lytic infection. To combat this, herpesviruses express endoribonucleases to deplete host RNAs. Here we demonstrate that IFN-induced circular RNAs (circRNAs) can escape viral-mediated degradation. We performed comparative circRNA expression profiling for representative alpha- (Herpes simplex virus-1, HSV-1), beta- (human cytomegalovirus, HCMV), and gamma-herpesviruses (Kaposi sarcoma herpesvirus, KSHV; murine gamma-herpesvirus 68, MHV68). Strikingly, we found that circRNAs are, as a population, resistant to host shutoff. This observation was confirmed by ectopic expression assays of human and murine herpesvirus endoribonucleases. During primary lytic infection, ten circRNAs were commonly regulated across all subfamilies of human herpesviruses, suggesting a common mechanism of regulation. We tested one such mechanism, namely how interferon-stimulation influences circRNA expression. 67 circRNAs were upregulated by either IFN-ß or -γ treatment, with half of these also upregulated during lytic infection. Using gain and loss of function studies we found an interferon-stimulated circRNA, circRELL1, inhibited lytic HSV-1 infection. We have previously reported circRELL1 inhibits lytic KSHV infection, suggesting a pan-herpesvirus antiviral activity. We propose a two-pronged model in which interferon-stimulated genes may encode both mRNA and circRNA with antiviral activity. This is critical in cases of host shutoff, such as alpha- and gamma-herpesvirus infection, where the mRNA products are degraded but circRNAs escape.

Chromatin Accessibility Landscape of Human Triple-negative Breast Cancer Cell Lines Reveals Variation by Patient Donor Ancestry.

African American (AA) women have an excessive risk of developing triple-negative breast cancer (TNBC). We employed Assay for Transposase-Accessible Chromatin using sequencing to characterize differences in chromatin accessibility between nine commonly used TNBC cell lines derived from patients of European and African ancestry. Principal component and chromosome mapping analyses of accessibility peaks with the most variance revealed separation of chromatin profiles by patient group. Motif enrichment and footprinting analyses of disparate open chromatin regions revealed differences in transcription factor activity, identifying 79 with ancestry-associated binding patterns (FDR < 0.01). AA TNBC cell lines exhibited increased accessibility for 62 transcription factors associated with epithelial-to-mesenchymal transition, cancer stemness/chemotherapeutic resistance, proliferation, and aberrant p53 regulation, as well as KAISO, which has been previously linked to aggressive tumor characteristics in AA patients with cancer. Differential Assay for Transposase-Accessible Chromatin signal analysis identified 1,596 genes located within promoters of differentially open chromatin regions in AA-derived TNBC, identifying DNA methyltransferase 1 as the top upregulated gene associated with African ancestry. Pathway analyses with these genes revealed enrichment in several pathways, including hypoxia. Culturing cells under hypoxia showed ancestry-specific stress responses that led to the identification of a core set of AA-associated transcription factors, which included members of the Kruppel-like factor and Sp subfamilies, as well as KAISO, and identified ZDHHC1, a gene previously implicated in immunity and STING activation, as the top upregulated AA-specific gene under hypoxia. Together, these data reveal a differential chromatin landscape in TNBC associated with donor ancestry. The open chromatin structure of AA TNBC may contribute to a more lethal disease. SIGNIFICANCE: We identify an ancestry-associated open chromatin landscape and related transcription factors that may contribute to aggressive TNBC in AA women. Furthermore, this study advocates for the inclusion of diversely sourced cell lines in experimental in vitro studies to advance health equity at all levels of scientific research.