Here we demonstrate that RNF4, a highly conserved small ubiquitin-like modifier (SUMO)-targeted ubiquitin E3 ligase, plays a critical role in the response of mammalian cells to DNA damage. Human cells in which RNF4 expression was ablated by siRNA or chicken DT40 cells with a homozygous deletion of the RNF4 gene displayed increased sensitivity to DNA-damaging agents. Recruitment of RNF4 to double-strand breaks required its RING and SUMO interaction motif (SIM) domains and DNA damage factors such as NBS1, mediator of DNA damage checkpoint 1 (MDC1), RNF8, 53BP1, and BRCA1. In the absence of RNF4, these factors were still recruited to sites of DNA damage, but 53BP1, RNF8, and RNF168 displayed delayed clearance from such foci. SILAC-based proteomics of SUMO substrates revealed that MDC1 was SUMO-modified in response to ionizing radiation. As a consequence of SUMO modification, MDC1 recruited RNF4, which mediated ubiquitylation at the DNA damage site. Failure to recruit RNF4 resulted in defective loading of replication protein A (RPA) and Rad51 onto ssDNA. This appeared to be a consequence of reduced recruitment of the CtIP nuclease, resulting in inefficient end resection. Thus, RNF4 is a novel DNA damage-responsive protein that plays a role in homologous recombination and integrates SUMO modification and ubiquitin signaling in the cellular response to genotoxic stress.[Keywords: RNF4; SUMO; ubiqutin; DNA damage] Supplemental material is available for this article. The integrity of the genome is under constant threat as intrinsic and extrinsic agents modify and break the DNA. If unrepaired, these toxic lesions can lead to cell death or induce chromosomal translocations and mutations that can ultimately lead to cancer. A double-strand break (DSB) is one of the most dangerous lesions that the genome can sustain, and such breaks can be generated by ionizing radiation (IR), as a consequence of damage during DNA replication, during recombinational rearrangement of the immunoglobulin genes, and in meiosis. Given the toxicity of DSBs, cells have evolved highly conserved and overlapping mechanisms to repair the damaged DNA. Homologous recombination (HR) and nonhomologous end-joining (NHEJ) are two distinct pathways that are differentially used during distinct phases of the cell cycle to repair DSBs.While repair of DNA damage via HR is highly accurate, NHEJ is regarded as operating at a lower fidelity. Although NHEJ is the predominant form of DSB repair in G1, it can function at any stage of the cell cycle, whereas HR functions predominantly in S/G2 and has a role in the repair of damaged replication forks. DSBs to be repaired by NHEJ are recognized and bound by the heterodimeric Ku protein, which allows recruitment and activation of the DNA-dependent protein kinase (DNA-PK). Tethering of active DNA-PK at the DNA ends allows assembly of a complex containing DNA ligase IV, XRCC4, and XLF/ Cernunnos protein, which ligates the DNA ends (Hiom 2010). As cells pass from S to G2 phase, the sister chromatid resulting from DNA replicat...

Performing axillary artery ultrasound in all patients with suspected temporal arteritis, PMR, arm claudication, unclear inflammation or PUO increases the diagnostic yield for LV-GCA. Patients with LV-GCA differ from those without arm involvement.

BACKGROUND: Molecular characterization of circulating tumor cells (CTCs) is pivotal to increasing the diagnostic specificity of CTC assays and investigating therapeutic targets and their downstream pathways on CTCs. We focused on epidermal growth factor receptor (EGFR) and genes relevant for its inhibition in patients with colorectal cancer (CRC).

Purpose Tyrosine kinase inhibitors are effective in gastrointestinal stromal tumor (GIST), but often are of transient benefit as resistance commonly develops. Immunotherapy, particularly blockade of the inhibitory receptor programmed death 1 (PD-1) or the ligand programmed death ligand 1 (PD-L1), has shown effectiveness in a variety of cancers. The functional effects of PD-1/PD-L1 blockade are unknown in GIST. Experimental Design We analyzed tumor and matched blood samples from 85 patients with GIST and determined the expression of immune checkpoint molecules using flow cytometry. We investigated the combination of imatinib with PD-1/PD-L1 blockade in KitV558Δ/+ mice that develop GIST. Results The inhibitory receptors PD-1, lymphocyte activation gene 3 (LAG-3), and T cell immunoglobulin mucin-3 (TIM-3) were upregulated on tumor-infiltrating T cells compared to T cells from matched blood. PD-1 expression on T cells was highest in imatinib-treated human GISTs. Meanwhile, intratumoral PD-L1 expression was variable. In human GIST cell lines, treatment with imatinib abrogated the IFN-γ–induced upregulation of PD-L1 via STAT1 inhibition. In KitV558Δ/+ mice imatinib downregulated IFN-γ–related genes and reduced PD-L1 expression on tumor cells. PD-1 and PD-L1 blockade in vivo each had no efficacy alone, but enhanced the antitumor effects of imatinib by increasing T cell effector function in the presence of KIT and IDO inhibition. Conclusions PD-1/PD-L1 blockade is a promising strategy to improve the effects of targeted therapy in GIST. Collectively, our results provide the rationale to combine these agents in human GIST.

Imatinib reduces tumor cell KIT signaling and causes tumor cell apoptosis, which drives TAMs to shift from M1- to M2-like in mouse and human GIST.

Hox genes are an evolutionary highly conserved gene family. They determine the anterior-posterior body axis in bilateral organisms and influence the developmental fate of cells. Embryonic stem cells are usually devoid of any Hox gene expression, but these transcription factors are activated in varying spatial and temporal patterns defining the development of various body regions. In the adult body, Hox genes are among others responsible for driving the differentiation of tissue stem cells towards their respective lineages in order to repair and maintain the correct function of tissues and organs. Due to their involvement in the embryonic and adult body, they have been suggested to be useable for improving stem cell differentiations in vitro and in vivo. In many studies Hox genes have been found as driving factors in stem cell differentiation towards adipogenesis, in lineages involved in bone and joint formation, mainly chondrogenesis and osteogenesis, in cardiovascular lineages including endothelial and smooth muscle cell differentiations, and in neurogenesis. As life expectancy is rising, the demand for tissue reconstruction continues to increase. Stem cells have become an increasingly popular choice for creating therapies in regenerative medicine due to their self-renewal and differentiation potential. Especially mesenchymal stem cells are used more and more frequently due to their easy handling and accessibility, combined with a low tumorgenicity and little ethical concerns. This review therefore intends to summarize to date known correlations between natural Hox gene expression patterns in body tissues and during the differentiation of various stem cells towards their respective lineages with a major focus on mesenchymal stem cell differentiations. This overview shall help to understand the complex interactions of Hox genes and differentiation processes all over the body as well as in vitro for further improvement of stem cell treatments in future regenerative medicine approaches.

Members of the ternary complex factor (TCF) subfamily of the ETS-domain transcription factors are activated through phosphorylation by mitogen-activated protein kinases (MAPKs) in response to a variety of mitogenic and stress stimuli. The TCFs bind and activate serum response elements (SREs) in the promoters of target genes in a ternary complex with a second transcription factor, serum response factor (SRF). The association of TCFs with SREs within immediate-early gene promoters is suggestive of a role for the ternary TCF-SRF complex in promoting cell cycle entry and proliferation in response to mitogenic signaling. Here we have investigated the downstream gene regulatory and phenotypic effects of inhibiting the activity of genes regulated by TCFs by expressing a dominantly acting repressive form of the TCF, Elk-1. Inhibition of ternary complex activity leads to the downregulation of several immediate-early genes. Furthermore, blocking TCFmediated gene expression leads to growth arrest and triggers apoptosis. By using mutant Elk-1 alleles, we demonstrated that these effects are via an SRF-dependent mechanism. The antiapoptotic gene Mcl-1 is identified as a key target for the TCF-SRF complex in this system. Thus, our data confirm a role for TCF-SRF-regulated gene activity in regulating proliferation and provide further evidence to indicate a role in protecting cells from apoptotic cell death.Elk-1 is a member of the ternary complex factor (TCF) subfamily of ETS-domain transcription factors (reviewed in references 46 and 50). In mammals there are two other TCFs, SAP-1 and SAP-2/ERP/Net. These proteins are characterized by their ability to form ternary complexes on target promoters in conjunction with the MADS-box protein serum response factor (SRF). The TCFs share four domains, the ETS DNAbinding domain, the B-box, the D-domain, and the C-domain. SAP-2/Net contains additional regions that impart repressive properties (9, 29). The D-and C-domains constitute the regulatory part of Elk-1 and other TCFs. The D-domain acts as a docking site for mitogen-activated protein kinases (MAPKs) (reviewed in references 15 and 49). These docked kinases can then phosphorylate residues in the C-domain, which constitutes the transcriptional activation domain (TAD). Phosphorylation of the TAD leads to elevation of the transactivation potential of the TCFs and also enhances ternary complex formation (reviewed in references 46, 50, 54, and 58). The TCFs can be phosphorylated by members of all three of the major MAPK pathways present in mammals: ERK, JNK, and p38 (reviewed in references 46, 50, and 58). The ERK MAPK pathway predominantly transmits mitogenic and differentiation stimuli, whereas the JNK and p38 MAPK pathways primarily transduce stress and cytokine stimuli to the nucleus (reviewed in reference 41). The TCFs therefore play a pivotal role in transducing extracellular stimuli into alterations in gene expression in the nucleus.The B-box of the TCFs is required for ternary complex formation (11,23,55) and mediates protein-prote...

The small ubiquitin-like modifier 2 (SUMO-2) is required for survival when cells are exposed to treatments that induce proteotoxic stress by causing the accumulation of misfolded proteins.Exposure of cells to heat shock or other forms of proteotoxic stress induces the conjugation of SUMO-2 to proteins in the nucleus. Here, we investigated the chromatin landscape of SUMO-2 modifications in response to heat stress. Through chromatin immunoprecipitation assays coupled to high-throughput DNA sequencing and with mRNA sequencing, we showed that in response to heat shock, SUMO-2 accumulated at nucleosome-depleted, active DNA-regulatory elements, which represented binding sites for large protein complexes and were predominantly associated with active genes. However, SUMO did not act as a direct transcriptional repressor or activator of these genes during heat shock. Instead, integration of our results with published proteomics data on heat shock-induced SUMO-2 substrates supports a model in which the conjugation of SUMO-2 to proteins acts as an acute stress response that is required for the stability of protein complexes involved in gene expression and posttranscriptional modification of mRNA. We showed that the conjugation of SUMO-2 to chromatin-associated proteins is an integral component of the proteotoxic stress response, and propose that SUMO-2 fulfills its essential role in cell survival by contributing to the maintenance of protein complex homeostasis.