Most eukaryotic mRNAs are translated using a cap-dependent mechanism of translation. However, approximately 10% of mammalian mRNAs initiate translation using a cap-independent mechanism that is not ...well understood. These mRNAs contain an internal ribosome entry site (IRES) located in the 5' untranslated region. The cricket paralysis virus (CrPV) intergenic region IRES (IGR IRES) functions in yeast, mammals, and plants, and does not require any translation initiation factors. We used yeast genetics to understand how ribosomes are recruited directly to the mRNA by an IRES. We found that Rps25p has an essential role in CrPV IGR IRES activity in yeast and mammalian cells but not in cap-dependent translation. Purified 40S ribosomal subunits lacking Rps25 are unable to bind to the IGR IRES in vitro. The hepatitis C virus (HCV) IRES also requires Rps25, demonstrating the function of Rps25 is conserved across IRES types. Yeast strains lacking Rps25 exhibit only slight defects in global translation, readthrough, ribosome biogenesis, and programmed ribosomal frameshifting. This work is the first demonstration of a ribosomal protein that is specifically required for IRES-mediated translation initiation. Our findings provide us with the beginnings of a model for the molecular interactions of an IRES with the ribosome.
HeLa is the most widely used model cell line for studying human cellular and molecular biology. To date, no genomic reference for this cell line has been released, and experiments have relied on the ...human reference genome. Effective design and interpretation of molecular genetic studies performed using HeLa cells require accurate genomic information. Here we present a detailed genomic and transcriptomic characterization of a HeLa cell line. We performed DNA and RNA sequencing of a HeLa Kyoto cell line and analyzed its mutational portfolio and gene expression profile. Segmentation of the genome according to copy number revealed a remarkably high level of aneuploidy and numerous large structural variants at unprecedented resolution. Some of the extensive genomic rearrangements are indicative of catastrophic chromosome shattering, known as chromothripsis. Our analysis of the HeLa gene expression profile revealed that several pathways, including cell cycle and DNA repair, exhibit significantly different expression patterns from those in normal human tissues. Our results provide the first detailed account of genomic variants in the HeLa genome, yielding insight into their impact on gene expression and cellular function as well as their origins. This study underscores the importance of accounting for the strikingly aberrant characteristics of HeLa cells when designing and interpreting experiments, and has implications for the use of HeLa as a model of human biology.
Abstract
Anti-cancer therapies often exhibit only short-term effects. Tumors typically develop drug resistance causing relapses that might be tackled with drug combinations. Identification of the ...right combination is challenging and would benefit from high-content, high-throughput combinatorial screens directly on patient biopsies. However, such screens require a large amount of material, normally not available from patients. To address these challenges, we present a scalable microfluidic workflow, called Combi-Seq, to screen hundreds of drug combinations in picoliter-size droplets using transcriptome changes as a readout for drug effects. We devise a deterministic combinatorial DNA barcoding approach to encode treatment conditions, enabling the gene expression-based readout of drug effects in a highly multiplexed fashion. We apply Combi-Seq to screen the effect of 420 drug combinations on the transcriptome of K562 cells using only ~250 single cell droplets per condition, to successfully predict synergistic and antagonistic drug pairs, as well as their pathway activities.
NUT carcinoma (NC) shows very aggressive clinical behavior, occurs predominantly in the thorax and head and neck region of children and adults, and is defined by the presence of NUT (aka NUTM1) ...rearrangement, mostly BRD4‐NUTM1 fusion resulting from t(15;19)(q13; p13.1). So‐called “NUT variants” harbor alternate fusions between NUTM1 and BRD3, NSD3, ZNF532, or unknown partners. Rare cases of pediatric tumors with CIC‐NUTM1 fusion were recently reported in somatic soft tissue, brain, and kidney. However, such cases have not been identified in adult patients and the presence of a fusion between CIC, characteristic of CIC‐rearranged sarcoma, and NUTM1—a defining feature of NC—poses a diagnostic challenge. We herein report a case of malignant epithelioid neoplasm with myoepithelial features harboring CIC‐NUTM1 fusion arising in soft tissue of the head in a 60‐year‐old man. Immunohistochemistry revealed strong expression of NUT, but only weak ETV4 staining and negativity for keratins, EMA, p40, CD99, and WT1. SMARCB1 expression was retained. Fluorescence in situ hybridization and targeted next‐generation sequencing identified a CIC‐NUTM1 fusion resulting from t(15;19)(q14;q13.2). In light of morphologic features that overlap with those of NC from typical anatomical sites we have seen previously, the tumor was best classified as falling within the NC spectrum rather than CIC‐associated sarcoma. This case highlights the emerging diagnostic challenges generated by newly detected gene fusions of unknown clinical and biologic significance. Careful integration of cytogenetic, molecular, and immunohistochemical findings with morphologic appearances in the diagnostic workup of undifferentiated neoplasms is essential.
Within the thymus, thymic epithelial cells (TECs) create dedicated microenvironments for T cell development and selection. Considering that TECs are sensitive to distinct pathophysiological ...conditions, uncovering the molecular elements that coordinate their thymopoietic role has important fundamental and clinical implications. Particularly, medullary thymic epithelial cells (mTECs) play a crucial role in central tolerance. Our previous studies, along with others, suggest that mTECs depend on molecular factors linked to genome-protecting pathways, but the precise mechanisms underlying their function remain unknown. These observations led us to examine the role of Foxo3, as it is expressed in TECs and involved in DNA damage response. Our findings show that mice with TEC-specific deletion of Foxo3 (Foxo3
) displayed a disrupted mTEC compartment, with a more profound impact on the numbers of CCL21
and thymic tuft mTEC
subsets. At the molecular level, Foxo3 controls distinct functional modules in the transcriptome of cTECs and mTECs under normal conditions, which includes the regulation of ribosomal biogenesis and DNA damage response, respectively. These changes in the TEC compartment resulted in a reduced total thymocyte cellularity and specific changes in regulatory T cell and iNKT cell development in the Foxo3
thymus. Lastly, the thymic defects observed in adulthood correlated with mild signs of altered peripheral immunotolerance in aged Foxo3
mice. Moreover, the deficiency in Foxo3 moderately aggravated the autoimmune predisposition observed in Aire-deficient mice. Our findings highlight the importance of Foxo3 in preserving the homeostasis of TECs and in supporting their role in T cell development and tolerance.
Effective management of a rapidly increasing juvenile green sea turtle Chelonia mydas population necessitates an understanding of the foraging grounds utilized throughout ontogeny. We used stomach ...content (SCA) and stable isotope analyses (SIA) of multiple size classes of green turtles foraging along the middle (MTC) and lower Texas coasts (LTC) in the northwestern Gulf of Mexico to identify ontogenetic shifts in foraging behavior. Spatial differences in diet and habitat residency were examined based on samples gathered from live (n = 55) and deceased turtles (n = 114). Additionally, the isotopic composition of putative forage material within nearshore and inshore habitats was investigated to determine prey contribution to diet. Green turtle recruitment to neritic channel environments in Texas waters at sizes <25 cm straight carapace length (SCL) was established based on the presence of benthic macroalgae in the diet. Integration of SCA with SIA of carbon and nitrogen in scute material, as well as potential prey, revealed a subsequent inshore shift to seagrass beds before obtaining 35 cm SCL for turtles of the LTC, while turtles from the MTC exhibited considerable variation in size at transition. This study improves our understanding of the feeding ecology of green turtles within critical foraging grounds along the Texas coast.
Mosquito blood cells are immune cells that help control infection by vector-borne pathogens. Despite their importance, little is known about mosquito blood cell biology beyond morphological and ...functional criteria used for their classification. Here, we combined the power of single-cell RNA sequencing, high-content imaging flow cytometry, and single-molecule RNA hybridization to analyze a subset of blood cells of the malaria mosquito Anopheles gambiae. By demonstrating that blood cells express nearly half of the mosquito transcriptome, our dataset represents an unprecedented view into their transcriptional program. Analyses of differentially expressed genes identified transcriptional signatures of two cell types and provide insights into the current classification of these cells. We further demonstrate the active transfer of a cellular marker between blood cells that may confound their identification. We propose that cell-to-cell exchange may contribute to cellular diversity and functional plasticity seen across biological systems.
The paucity of microbiome studies at intestinal tissues has contributed to a yet limited understanding of potential viral and bacterial cofactors of colorectal cancer (CRC) carcinogenesis or ...progression. We analysed whole‐genome sequences of CRC primary tumours, their corresponding metastases and matched normal tissue for sequences of viral, phage and bacterial species. Bacteriome analysis showed Fusobacterium nucleatum, Streptococcus sanguinis, F. Hwasookii, Anaerococcus mediterraneensis and further species enriched in primary CRCs. The primary CRC of one patient was enriched for F. alocis, S. anginosus, Parvimonas micra and Gemella sp. 948. Enrichment of Escherichia coli strains IAI1, SE11, K‐12 and M8 was observed in metastases together with coliphages enterobacteria phage φ80 and Escherichia phage VT2φ_272. Virome analysis showed that phages were the most preponderant viral species (46%), the main families being Myoviridae, Siphoviridae and Podoviridae. Primary CRCs were enriched for bacteriophages, showing five phages (Enterobacteria, Bacillus, Proteus, Streptococcus phages) together with their pathogenic hosts in contrast to normal tissues. The most frequently detected, and Blast‐confirmed, viruses included human endogenous retrovirus K113, human herpesviruses 7 and 6B, Megavirus chilensis, cytomegalovirus (CMV) and Epstein–Barr virus (EBV), with one patient showing EBV enrichment in primary tumour and metastases. EBV was PCR‐validated in 80 pairs of CRC primary tumour and their corresponding normal tissues; in 21 of these pairs (26.3%), it was detectable in primary tumours only. The number of viral species was increased and bacterial species decreased in CRCs compared with normal tissues, and we could discriminate primary CRCs from metastases and normal tissues by applying the Hutcheson t‐test on the Shannon indices based on viral and bacterial species. Taken together, our results descriptively support hypotheses on microorganisms as potential (co)risk factors of CRC and extend putative suggestions on critical microbiome species in CRC metastasis.
This work analysed the presence of sequences of bacteria and viruses in primary colorectal cancer (CRC) tissues, compared with corresponding normal colorectal tissues and metastases. We observed a higher viral species diversity and lower bacterial species diversity in primary CRCs than in matched normal tissues. Some microbial species were enriched in primary CRCs and some metastases, particularly phages.
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