The activation-induced expression of DHX32 in Jurkat T cells is specific and involves calcium and nuclear factor of activated T cells

Structure and function of DEAH-box helicase 32 and its role in cancer

DEAH-box helicase 32 (DHX32) is an RNA helicase with unique structural characteristics that is involved in numerous biological processes associated with RNA, including ribosome biosynthesis, transcription, mRNA splicing and translation. Increasing evidence suggests that abnormal DHX32 expression contributes to cancer initiation and development, due to dysregulated cell proliferation, differentiation, apoptosis and other processes. In the current review, the discovery, structure and function of DHX32, as well as the association between abnormal DHX32 expression and tumors are discussed. DHX32 expression is downregulated in acute lymphoblastic leukemia, but upregulated in solid tumors, including colorectal and breast cancer. Furthermore, DHX32 expression levels are associated with the pathological and clinical features of the cancer. Therefore, DHX32 may serve as a novel liquid biopsy marker for auxiliary diagnosis and prognosis screening, as well as a possible target for cancer therapy. The molecular mechanism underlying the contribution of DHX32 towards the initiation and development of cancer requires further investigation for the development of anticancer treatments based on manipulating DHX32 expression and function.

Variation at FCGR2A and functionally related genes is associated with the response to anti-TNF therapy in rheumatoid arthritis

Objective

Anti-TNF therapies have been highly efficacious in the management of rheumatoid arthritis (RA), but 25–30% of patients do not show a significant clinical response. There is increasing evidence that genetic variation at the Fc receptor FCGR2A is associated with the response to anti-TNF therapy. We aimed to validate this genetic association in a patient cohort from the Spanish population, and also to identify new genes functionally related to FCGR2A that are also associated with anti-TNF response.

Methods

A total of 348 RA patients treated with an anti-TNF therapy were included and genotyped for FCGR2A polymorphism rs1081274. Response to therapy was determined at 12 weeks, and was tested for association globally and independently for each anti-TNF drug (infliximab, etanercept and adalimumab). Using gene expression profiles from macrophages obtained from synovial fluid of RA patients, we searched for genes highly correlated with FCGR2A expression. Tag SNPs were selected from each candidate gene and tested for association with the response to therapy.

Results

We found a significant association between FCGR2A and the response to adalimumab (P=0.022). Analyzing the subset of anti-CCP positive RA patients (78%), we also found a significant association between FCGR2A and the response to infliximab (P=0.035). DHX32 and RGS12 were the most consistently correlated genes with FCGR2A expression in RA synovial fluid macrophages (P<0.001). We found a significant association between the genetic variation at DHX32 (rs12356233, corrected P=0.019) and a nominally significant association between RGS12 and the response to adalimumab (rs4690093, uncorrected P=0.040). In the anti-CCP positive group of patients, we also found a nominally significant association between RGS12 and the response to infliximab (rs2857859, uncorrected P=0.042).

Conclusions

In the present study we have validated the FCGR2A association in an independent population, and we have identified new genes associated with the response to anti-TNF therapy in RA.

A human XPC protein interactome--a resource

Global genome nucleotide excision repair (GG-NER) is responsible for identifying and removing bulky adducts from non-transcribed DNA that result from damaging agents such as UV radiation and cisplatin. Xeroderma pigmentosum complementation group C (XPC) is one of the essential damage recognition proteins of the GG-NER pathway and its dysfunction results in xeroderma pigmentosum (XP), a disorder involving photosensitivity and a predisposition to cancer. To better understand the identification of DNA damage by XPC in the context of chromatin and the role of XPC in the pathogenesis of XP, we characterized the interactome of XPC using a high throughput yeast two-hybrid screening. Our screening showed 49 novel interactors of XPC involved in DNA repair and replication, proteolysis and post-translational modifications, transcription regulation, signal transduction, and metabolism. Importantly, we validated the XPC-OTUD4 interaction by co-IP and provided evidence that OTUD4 knockdown in human cells indeed affects the levels of ubiquitinated XPC, supporting a hypothesis that the OTUD4 deubiquitinase is involved in XPC recycling by cleaving the ubiquitin moiety. This high-throughput characterization of the XPC interactome provides a resource for future exploration and suggests that XPC may have many uncharacterized cellular functions.

Altered distribution of heat shock protein 60 (Hsp60) with dysregulated expression of DHX32

DHX32 has an overall similarity to the DHX family of RNA helicases but with a novel helicase domain and nuclear and mitochondrial localizations. The expression of DHX32 is highly regulated during lymphocyte activation and is dysregulated in lymphoid malignancies. In this study, we report our finding of an altered subcellular localization of heat shock protein 60 (Hsp60) in Jurkat-DHX32 cell line in which DHX32 is constitutively expressed. Two-dimensional gel electrophoresis followed by mass spectrometry, electron microscopic immunocytochemistry, and immunoblot analysis showed mainly cytoplasmic localization of Hsp60 in Jurkat-DHX32 cells instead of its mainly mitochondrial localization in control cells. No significant changes were detected in the mitochondrial ultra-structure and the mitochondrial membrane potential activity as a result of dysregulated DHX32 expression. The subcellular distribution of several mitochondrial proteins including cytochrome c, peroxiredoxin 3, manganese superoxide dismutase, Leucine-Rich PentatricoPeptide Repeat Cassette and the 49-kDa subunit of the mitochondrial respiratory Complex I were similar in control and Jurkat-DHX32 cells ruling out non-specific cytoplasmic leakage of mitochondrial proteins. No significant changes in the expression of Hsp60 transcript or total cellular protein were detected. These findings suggest that dysregulated expression of DHX32 might lead to as of yet unknown changes in mitochondrial homeostasis manifested by cytoplasmic redistribution of the molecular chaperon Hsp60.

Runx-dependent regulation of G-protein gamma3 expression in T-cells

Heterotrimeric G-proteins control diverse biological processes by conveying signals from seven-transmembrane receptors to intracellular effectors. Although their signaling roles were originally ascribed to their GTP-bound alpha-subunits, more recent evidence points to the equally active roles played by their betagamma-dimers. To elucidate the individual contributions of their gamma-subtypes, we used a gene targeting approach to show that mice lacking the gamma3-subtype display a defective T-cell dependent immune response. To identify the cellular basis for this defect, we demonstrated that gamma3-mRNA is strongly induced in activated CD4+ T-cells. To determine the mechanism for this regulated expression, we used several strategies to identify the importance of a Runx consensus sequence element in the first intron of the gamma3 gene and the Runx1 protein. Overall, these data provide the first genetic evidence for the tight regulation and involvement of the G protein gamma3-subtype in mounting an effective immune response in mice.