Search

Abstract Spatial organization and gene expression of mammalian chromosomes are maintained and regulated in conjunction with cell cycle progression. This is perturbed once cells enter senescence and the highly abundant HMGB1 protein is depleted from nuclei to act as an extracellular proinflammatory stimulus. Despite its physiological importance, we know little about the positioning of HMGB1 on chromatin and its nuclear roles. To address this, we mapped HMGB1 binding genome‐wide in two primary cell lines. We integrated ChIP‐seq and Hi‐C with graph theory to uncover clustering of HMGB1‐marked topological domains that harbor genes involved in paracrine senescence. Using simplified Cross‐Linking and Immuno‐Precipitation and functional tests, we show that HMGB1 is also a bona fide RNA‐binding protein (RBP) binding hundreds of mRNAs. It presents an interactome rich in RBPs implicated in senescence regulation. The mRNAs of many of these RBPs are directly bound by HMGB1 and regulate availability of SASP‐relevant transcripts. Our findings reveal a broader than hitherto assumed role for HMGB1 in coordinating chromatin folding and RNA homeostasis as part of a regulatory loop controlling cell‐autonomous and paracrine senescence.

Abstract Innate immunity triggers responsible for viral control or hyperinflammation in COVID‐19 are largely unknown. Here we show that the SARS‐CoV‐2 spike protein (S‐protein) primes inflammasome formation and release of mature interleukin‐1β (IL‐1β) in macrophages derived from COVID‐19 patients but not in macrophages from healthy SARS‐CoV‐2 naïve individuals. Furthermore, longitudinal analyses reveal robust S‐protein‐driven inflammasome activation in macrophages isolated from convalescent COVID‐19 patients, which correlates with distinct epigenetic and gene expression signatures suggesting innate immune memory after recovery from COVID‐19. Importantly, we show that S‐protein‐driven IL‐1β secretion from patient‐derived macrophages requires non‐specific monocyte pre‐activation in vivo to trigger NLRP3‐inflammasome signaling. Our findings reveal that SARS‐CoV‐2 infection causes profound and long‐lived reprogramming of macrophages resulting in augmented immunogenicity of the SARS‐CoV‐2 S‐protein, a major vaccine antigen and potent driver of adaptive and innate immune signaling.

Abstract Functional studies giving insight into the biology of circulating tumor cells (CTCs) remain scarce due to the low frequency of CTCs and lack of appropriate models. Here, we describe the characterization of a novel CTC‐derived breast cancer cell line, designated CTC‐ITB‐01, established from a patient with metastatic estrogen receptor‐positive (ER+) breast cancer, resistant to endocrine therapy. CTC‐ITB‐01 remained ER+ in culture, and copy number alteration (CNA) profiling showed high concordance between CTC‐ITB‐01 and CTCs originally present in the patient with cancer at the time point of blood draw. RNA‐sequencing data indicate that CTC‐ITB‐01 has a predominantly epithelial expression signature. Primary tumor and metastasis formation in an intraductal PDX mouse model mirrored the clinical progression of ER+ breast cancer. Downstream ER signaling was constitutively active in CTC‐ITB‐01 independent of ligand availability, and the CDK4/6 inhibitor Palbociclib strongly inhibited CTC‐ITB‐01 growth. Thus, we established a functional model that opens a new avenue to study CTC biology.