Genes & Development
ISSN / EISSN : 0890-9369 / 1549-5477
Published by: Cold Spring Harbor Laboratory (10.1101)
Total articles ≅ 8,547
Latest articles in this journal
Genes & Development; https://doi.org/10.1101/gad.349550.122
Self-renewal of spermatogonial stem cells is vital to lifelong production of male gametes and thus fertility. However, the underlying mechanisms remain enigmatic. Here, we show that DOT1L, the sole H3K79 methyltransferase, is required for spermatogonial stem cell self-renewal. Mice lacking DOT1L fail to maintain spermatogonial stem cells, characterized by a sequential loss of germ cells from spermatogonia to spermatids and ultimately a Sertoli cell only syndrome. Inhibition of DOT1L reduces the stem cell activity after transplantation. DOT1L promotes expression of the fate-determining HoxC transcription factors in spermatogonial stem cells. Furthermore, H3K79me2 accumulates at HoxC9 and HoxC10 genes. Our findings identify an essential function for DOT1L in adult stem cells and provide an epigenetic paradigm for regulation of spermatogonial stem cells.
Genes & Development; https://doi.org/10.1101/gad.349412.122
The progeny of intestinal stem cells (ISCs) dedifferentiate in response to ISC attrition. The precise cell sources, transitional states, and chromatin remodeling behind this activity remain unclear. In the skin, stem cell recovery after injury preserves an epigenetic memory of the damage response; whether similar memories arise and persist in regenerated ISCs is not known. We addressed these questions by examining gene activity and open chromatin at the resolution of single Neurog3-labeled mouse intestinal crypt cells, hence deconstructing forward and reverse differentiation of the intestinal secretory (Sec) lineage. We show that goblet, Paneth, and enteroendocrine cells arise by multilineage priming in common precursors, followed by selective access at thousands of cell-restricted cis-elements. Selective ablation of the ISC compartment elicits speedy reversal of chromatin and transcriptional features in large fractions of precursor and mature crypt Sec cells without obligate cell cycle re-entry. ISC programs decay and reappear along a cellular continuum lacking discernible discrete interim states. In the absence of gross tissue damage, Sec cells simply reverse their forward trajectories, without invoking developmental or other extrinsic programs, and starting chromatin identities are effectively erased. These findings identify strikingly plastic molecular frameworks in assembly and regeneration of a self-renewing tissue.
Genes & Development; https://doi.org/10.1101/gad.348982.121
Chromosomal translocations frequently promote carcinogenesis by producing gain-of-function fusion proteins. Recent studies have identified highly recurrent chromosomal translocations in patients with endometrial stromal sarcomas (ESSs) and ossifying fibromyxoid tumors (OFMTs), leading to an in-frame fusion of PHF1 (PCL1) to six different subunits of the NuA4/TIP60 complex. While NuA4/TIP60 is a coactivator that acetylates chromatin and loads the H2A.Z histone variant, PHF1 is part of the Polycomb repressive complex 2 (PRC2) linked to transcriptional repression of key developmental genes through methylation of histone H3 on lysine 27. In this study, we characterize the fusion protein produced by the EPC1-PHF1 translocation. The chimeric protein assembles a megacomplex harboring both NuA4/TIP60 and PRC2 activities and leads to mislocalization of chromatin marks in the genome, in particular over an entire topologically associating domain including part of the HOXD cluster. This is linked to aberrant gene expression—most notably increased expression of PRC2 target genes. Furthermore, we show that JAZF1—implicated with a PRC2 component in the most frequent translocation in ESSs, JAZF1-SUZ12—is a potent transcription activator that physically associates with NuA4/TIP60, its fusion creating outcomes similar to those of EPC1-PHF1. Importantly, the specific increased expression of PRC2 targets/HOX genes was also confirmed with ESS patient samples. Altogether, these results indicate that most chromosomal translocations linked to these sarcomas use the same molecular oncogenic mechanism through a physical merge of NuA4/TIP60 and PRC2 complexes, leading to mislocalization of histone marks and aberrant Polycomb target gene expression.
Genes & Development; https://doi.org/10.1101/gad.349489.122
How distal regulatory elements control gene transcription and chromatin topology is not clearly defined, yet these processes are closely linked in lineage specification during development. Through allele-specific genome editing and chromatin interaction analyses of the Sox2 locus in mouse embryonic stem cells, we found a striking disconnection between transcriptional control and chromatin architecture. We traced nearly all Sox2 transcriptional activation to a small number of key transcription factor binding sites, whose deletions have no effect on promoter–enhancer interaction frequencies or topological domain organization. Local chromatin architecture maintenance, including at the topologically associating domain (TAD) boundary downstream from the Sox2 enhancer, is widely distributed over multiple transcription factor-bound regions and maintained in a CTCF-independent manner. Furthermore, partial disruption of promoter–enhancer interactions by ectopic chromatin loop formation has no effect on Sox2 transcription. These findings indicate that many transcription factors are involved in modulating chromatin architecture independently of CTCF.
Genes & Development, Volume 36, pp 634-646; https://doi.org/10.1101/gad.349488.122
In response to starvation, endospore-forming bacteria differentiate into stress-resistant spores that can remain dormant for years yet rapidly germinate and resume growth in response to nutrients. The small molecule dipicolinic acid (DPA) plays a central role in both the stress resistance of the dormant spore and its exit from dormancy during germination. The spoVA locus is required for DPA import during sporulation and has been implicated in its export during germination, but the molecular bases are unclear. Here, we define the minimal set of proteins encoded in the Bacillus subtilis spoVA operon required for DPA import and demonstrate that these proteins form a membrane complex. Structural modeling of these components combined with mutagenesis and in vivo analysis reveal that the C and Eb subunits form a membrane channel, while the D subunit functions as a cytoplasmic plug. We show that point mutations that impair the interactions between D and the C–Eb membrane complex reduce the efficiency of DPA import during sporulation and reciprocally accelerate DPA release during germination. Our data support a model in which DPA transport into spores involves cycles of unplugging and then replugging the C–Eb membrane channel, while nutrient detection during germination triggers DPA release by unplugging it.
Genes & Development, Volume 36, pp 566-581; https://doi.org/10.1101/gad.349393.122
Accumulation of fat above the waist is an important risk factor in developing obesity-related comorbidities independently of BMI or total fat mass. Deciphering the gene regulatory programs of the adipose tissue precursor cells within upper body or abdominal (ABD) and lower body or gluteofemoral (GF) depots is important to understand their differential capacity for lipid accumulation, maturation, and disease risk. Previous studies identified the HOX transcript antisense intergenic RNA (HOTAIR) as a GF-specific lncRNA; however, its role in adipose tissue biology is still unclear. Using three different approaches (silencing of HOTAIR in GF human adipose-derived stem cells [GF hASCs], overexpression of HOTAIR in ABD hASCs, and ChIRP-seq) to localize HOTAIR binding in GF hASC chromatin, we found that HOTAIR binds and modulates expression, both positively and negatively, of genes involved in adipose tissue-specific pathways, including adipogenesis. We further demonstrate a direct interaction between HOTAIR and genes with high RNAPII binding in their gene bodies, especially at their 3′ ends or transcription end sites. Computational analysis suggests HOTAIR binds preferentially to the 3′ ends of genes containing predicted strong RNA–RNA interactions with HOTAIR. Together, these results reveal a unique function for HOTAIR in hASC depot-specific regulation of gene expression.
Genes & Development, Volume 36, pp 533-549; https://doi.org/10.1101/gad.349585.122
Senescence is a stress-responsive tumor suppressor mechanism associated with expression of the senescence-associated secretory phenotype (SASP). Through the SASP, senescent cells trigger their own immune-mediated elimination, which if evaded leads to tumorigenesis. Senescent parenchymal cells are separated from circulating immunocytes by the endothelium, which is targeted by microenvironmental signaling. Here we show that SASP induces endothelial cell NF-κB activity and that SASP-induced endothelial expression of the canonical NF-κB component Rela underpins senescence surveillance. Using human liver sinusoidal endothelial cells (LSECs), we show that SASP-induced endothelial NF-κB activity regulates a conserved transcriptional program supporting immunocyte recruitment. Furthermore, oncogenic hepatocyte senescence drives murine LSEC NF-κB activity in vivo. Critically, we show two distinct endothelial pathways in senescence surveillance. First, endothelial-specific loss of Rela prevents development of Stat1-expressing CD4+ T lymphocytes. Second, the SASP up-regulates ICOSLG on LSECs, with the ICOS–ICOSLG axis contributing to senescence cell clearance. Our results show that the endothelium is a nonautonomous SASP target and an organizing center for immune-mediated senescence surveillance.
Genes & Development, Volume 36, pp 582-600; https://doi.org/10.1101/gad.349321.121
One of the mechanisms by which cancer cells acquire hyperinvasive and migratory properties with progressive loss of epithelial markers is the epithelial-to-mesenchymal transition (EMT). We have previously reported that in different cancer types, including nonsmall cell lung cancer (NSCLC), the microRNA-183/96/182 cluster (m96cl) is highly repressed in cells that have undergone EMT. In the present study, we used a novel conditional m96cl mouse to establish that loss of m96cl accelerated the growth of Kras mutant autochthonous lung adenocarcinomas. In contrast, ectopic expression of the m96cl in NSCLC cells results in a robust suppression of migration and invasion in vitro, and tumor growth and metastasis in vivo. Detailed immune profiling of the tumors revealed a significant enrichment of activated CD8+ cytotoxic T lymphocytes (CD8+ CTLs) in m96cl-expressing tumors, and m96cl-mediated suppression of tumor growth and metastasis was CD8+ CTL-dependent. Using coculture assays with naïve immune cells, we show that m96cl expression drives paracrine stimulation of CD8+ CTL proliferation and function. Using tumor microenvironment-associated gene expression profiling, we identified that m96cl elevates the interleukin-2 (IL2) signaling pathway and results in increased IL2-mediated paracrine stimulation of CD8+ CTLs. Furthermore, we identified that the m96cl modulates the expression of IL2 in cancer cells by regulating the expression of transcriptional repressors Foxf2 and Zeb1, and thereby alters the levels of secreted IL2 in the tumor microenvironment. Last, we show that in vivo depletion of IL2 abrogates m96cl-mediated activation of CD8+ CTLs and results in loss of metastatic suppression. Therefore, we have identified a novel mechanistic role of the m96cl in the suppression of lung cancer growth and metastasis by inducing an IL2-mediated systemic CD8+ CTL immune response.
Genes & Development, Volume 36, pp 601-617; https://doi.org/10.1101/gad.349335.121
The differentiation of embryonic stem cells (ESCs) into a lineage-committed state is a dynamic process involving changes in cellular metabolism, epigenetic modifications, post-translational modifications, gene expression, and RNA processing. Here we integrated data from metabolomic, proteomic, and transcriptomic assays to characterize how alterations in NAD+ metabolism during the differentiation of mouse ESCs lead to alteration of the PARP1-mediated ADP-ribosylated (ADPRylated) proteome and mRNA isoform specialization. Our metabolomic analyses indicate that mESCs use distinct NAD+ biosynthetic pathways in different cell states: the de novo pathway in the pluripotent state, and the salvage and Preiss–Handler pathways as differentiation progresses. We observed a dramatic induction of PARP1 catalytic activity driven by enhanced nuclear NAD+ biosynthesis during the early stages of mESC differentiation (e.g., within 12 h of LIF removal). PARP1-modified proteins in mESCs are enriched for biological processes related to stem cell maintenance, transcriptional regulation, and RNA processing. The PARP1 substrates include core spliceosome components, such as U2AF35 and U2AF65, whose splicing functions are modulated by PARP1-mediated site-specific ADP-ribosylation. Finally, we observed that splicing is dysregulated genome-wide in Parp1 knockout mESCs. Together, these results demonstrate a role for the NAD+–PARP1 axis in the maintenance of mESC state, specifically in the splicing program during differentiation.
Genes & Development, Volume 36, pp 550-565; https://doi.org/10.1101/gad.349456.122
Although splicing is a major driver of RNA nuclear export, many intronless RNAs are efficiently exported to the cytoplasm through poorly characterized mechanisms. For example, GC-rich sequences promote nuclear export in a splicing-independent manner, but how GC content is recognized and coupled to nuclear export is unknown. Here, we developed a genome-wide screening strategy to investigate the mechanism of export of NORAD, an intronless cytoplasmic long noncoding RNA (lncRNA). This screen revealed an RNA binding protein, RBM33, that directs the nuclear export of NORAD and numerous other transcripts. RBM33 directly binds substrate transcripts and recruits components of the TREX–NXF1/NXT1 RNA export pathway. Interestingly, high GC content emerged as the feature that specifies RBM33-dependent nuclear export. Accordingly, RBM33 directly binds GC-rich elements in target transcripts. These results provide a broadly applicable strategy for the genetic dissection of nuclear export mechanisms and reveal a long-sought nuclear export pathway for transcripts with GC-rich sequences.