Biology subjects

Hobbs, R. P.

Publications and source records attributed to Hobbs, R. P..

3 recordsLinked to original sources

bioRxiv2020

DOT1L modulates the senescence-associated secretory phenotype through epigenetic regulation of IL1A

Cellular senescence is characterized as a stable cell cycle arrest that can occur as a stress response associated with oncogenic activation, termed oncogene-induced senescence (OIS). Cells undergoing OIS acquire a unique microenvironment termed the senescence-associated secretory phenotype (SASP), which can be both beneficial and detrimental in a context-dependent manner. Additionally, senescent cells are characterized by robust changes in their epigenome. Here, we globally assessed the histone landscape of cells induced to senesce by oncogenic RAS and discovered a novel epigenetic regulatory mechanism of the key SASP regulator IL1A. OIS cells displayed increased di- and tri-methylation of histone H3 lysine 79 (H3K79me2/3), two active histone marks. Depletion of the H3K79 methyltransferase disruptor of telomeric silencing 1-like (DOT1L) during OIS resulted in decreased H3K79me2/3 occupancy at the IL1A gene locus, which corresponded to decreased IL1A mRNA and cell surface expression. Decreased expression and secretion of downstream cytokines without a change in senescence markers were also observed upon DOT1L depletion. Overexpression of DOT1L increased H3K79me2/3 occupancy at the IL1A locus and upregulated the SASP, indicating that DOT1L is both necessary and sufficient for SASP gene expression. Mechanistically, we found that STING, an essential mediator of SASP transcription, is upstream of DOT1L in the epigenetic regulation of the SASP. Together, our studies establish DOT1L as an epigenetic regulator of the SASP whose expression is uncoupled from the senescence-associated cell cycle arrest, providing a potential strategy to inhibit the negative side effects of senescence while maintaining the beneficial inhibition of proliferation.

cell biology↗

bioRxiv2020

Keratin 17 regulates nuclear morphology and chromatin organization

Keratin 17 (KRT17; K17), a non-lamin intermediate filament protein, was recently found to occur in the nucleus. We report here on K17-dependent differences in nuclear morphology, chromatin organization, and cell proliferation. Human tumor keratinocyte cell lines lacking K17 exhibit flatter nuclei relative to normal. Re-expression of wildtype K17, but not a mutant form lacking an intact nuclear localization signal (NLS), rescues nuclear morphology in KRT17 null cells. Analyses of primary cultures of skin keratinocytes from a mouse strain expressing K17 with a mutated NLS corroborated these findings. Proteomics screens identified K17-interacting nuclear proteins with known roles in gene expression, chromatin organization, and RNA processing. Key histone modifications and LAP2{beta} localization within the nucleus are altered in the absence of K17, correlating with decreased cell proliferation and suppression of GLI1 target genes. Nuclear K17 thus impacts nuclear morphology with an associated impact on chromatin organization, gene expression, and proliferation in epithelial cells. SummaryKeratin 17 (K17) is one of two non-lamin intermediate filament proteins recently identified to localize to and function in the cell nucleus. K17 is here shown to regulate nuclear morphology, chromatin organization, LAP2 localization, and cell proliferation.

cell biology↗

bioRxiv2019

Type I interferon-dependent CCL4 is induced by a cGAS/STING pathway that bypasses viral inhibition and protects infected tissue, independent of viral burden

Type I interferons (T1-IFN) are critical in the innate immune response, acting upon infected and uninfected cells to initiate an antiviral state by expressing genes that inhibit multiple stages of the lifecycle of many viruses. T1-IFN triggers the production of Interferon-Stimulated Genes (ISGs), activating an antiviral program that reduces virus replication. The importance of the T1-IFN response is highlighted by the evolution of viral evasion strategies to inhibit the production or action of T1-IFN in virus-infected cells. T1-IFN is produced via activation of pathogen sensors within infected cells, a process that is targeted by virus-encoded immunomodulatory molecules. This is probably best exemplified by the prototypic poxvirus, Vaccinia virus (VACV), which uses at least 6 different mechanisms to completely block the production of T1-IFN within infected cells in vitro. Yet, mice lacking aspects of T1-IFN signaling are often more susceptible to infection with many viruses, including VACV, than wild-type mice. How can these opposing findings be rationalized? The cytosolic DNA sensor cGAS has been implicated in immunity to VACV, but has yet to be linked to the production of T1-IFN in response to VACV infection. Indeed, there are two VACV-encoded proteins that effectively prevent cGAS-mediated activation of T1-IFN. We find that the majority of VACV-infected cells in vivo do not produce T1-IFN, but that a small subset of VACV-infected cells in vivo utilize cGAS to sense VACV and produce T1-IFN to protect infected mice. The protective effect of T1-IFN is not mediated via ISG-mediated control of virus replication. Rather, T1-IFN drives expression of CCL4, which recruits inflammatory monocytes that constrain the VACV lesion in a virus replication-independent manner by limiting spread within the tissue. Our findings have broad implications in our understanding of pathogen detection and viral evasion in vivo, and highlight a novel immune strategy to protect infected tissue.\n\nSummaryThe recognition of virus infection leads to a quick and robust antiviral response mediated by type I interferons (T1-IFN). Nearly all viruses have acquired genes that block the induction or action of T1-IFN in order to attain a replicative advantage. Some viruses thwart the T1-IFN response so thoroughly, that cells infected in vitro do not produce any T1-IFN. And yet, animal models with defects in T1-IFN signaling are more sensitive to infection with these viruses than their wild-type counterparts. In this study, we find evidence to explain these otherwise contradicting findings. We show that a small population of infected cells in vivo are able to utilize a pathogen-sensing pathway that is completely blocked in vitro. T1-IFN produced by these specialized cells protects mice by recruiting inflammatory monocytes that restrict the spread of virus within infected tissue, independent of viral burden. Our findings have a direct impact on our understanding of how viruses are detected in infected tissue, and present a novel strategy of the immune system to limit pathology at peripheral sites of infection.

immunology↗