The p53-inducible gene 3 (PIG3) is originally isolated as a p53 downstream target gene, but its function remains unknown. Here, we report a role of PIG3 in the activation of DNA damage checkpoints, after UV irradiation or radiomimetic drug neocarzinostatin (NCS). We show that depletion of endogenous PIG3 sensitizes cells to DNA damage agents, and impaired DNA repair. PIG3 depletion also allows for UV-and NCS-resistant DNA synthesis and permits cells to progress into mitosis, indicating that PIG3 knockdown can suppress intra-S phase and G2/M checkpoints. PIG3-depleted cells show reduced Chk1 and Chk2 phosphorylation after DNA damage, which may directly contribute to checkpoint bypass. PIG3 exhibited diffuse nuclear staining in the majority of untreated cells and forms discrete nuclear foci in response to DNA damage. PIG3 colocalizes with c-H2AX and 53BP1 to sites of DNA damage after DNA damage, and binds to a c-H2AX. Notably, PIG3 depletion decreases the efficient induction and maintenance of H2AX phosphorylation after DNA damage. Moreover, PIG3 contributes to the recruitment of 53BP1, Mre11, Rad50 and Nbs1 to the sites of DNA break lesions in response to DNA damage. Our combined results suggest that PIG3 is a critical component of the DNA damage response pathway and has a direct role in the transmission of the DNA damage signal from damaged DNA to the intra-S and G2/M checkpoint machinery in human cells.

Edited by Dennis VoelkerMesenchymal stromal cells (MSCs) present in the bone marrow microenvironment secrete cytokines and angiogenic factors that support the maintenance and regenerative expansion of hematopoietic stem and progenitor cells (HSPCs). Here, we tested the hypothesis that extracellular vesicles (EVs) released by MSCs contribute to the paracrine crosstalk that shapes hematopoietic function. We systematically characterized EV release by murine stromal cells and demonstrate that MSC-derived EVs prompt a loss of HSPC quiescence with concomitant expansion of murine myeloid progenitors. Our studies reveal that HSPC expansion by MSC EVs is mediated via the MyD88 adapter protein and is partially blocked by treatment with a TLR4 inhibitor. Imaging of fluorescence protein-tagged MSC EVs corroborated their cellular co-localization with TLR4 and endosomal Rab5 compartments in HSPCs. The dissection of downstream responses to TLR4 activation reveals that the mechanism by which MSC EVs impact HSPCs involves canonical NF-B signaling and downstream activation of Hif-1␣ and CCL2 target genes. Our aggregate data identify a previously unknown role for MSC-derived EVs in the regulation of hematopoiesis through innate immune mechanisms and illustrate the expansive cell-cell crosstalk in the bone marrow microenvironment.A small population of long-lived quiescent HSPCs 3 residing in the bone marrow sustains lifelong hematopoietic function and provides regenerative capacity through cycles of self-renewal and differentiation (1). Cell fate commitment yields a cascade of successively more restricted progenitor populations that give rise to circulating blood and mature immune cells (2). HSPC activation relies on cell-autonomous programs as well as extrinsic cues from the surrounding bone marrow microenvironment where mesenchymal stromal cells, osteoprogenitors, and endothelial cells act through the paracrine action of secreted cytokines and angiogenic factors (3-6).Recent studies indicate that HSPC self-renewal and emergence from quiescence are also regulated by type I and II interferons as well as Toll-like receptors (TLRs), signals associated with innate immunity (7-10), and known to contribute to regenerative HSPC responses (11)(12)(13)(14)(15). TLR signaling involves a number of transmembrane receptors and several critical adaptor molecules (16). Among them, the myeloid differentiation factor (MyD88) occupies a central role in transducing both surface and endosomal signals for most TLRs. Evidence supports TLR activation in the HSPC response to diverse stimuli, including radiation, bleeding, and infection (reviewed in Ref. 12). More recent reports, however, indicate that these mechanisms are also relevant for "tonic" homeostatic function and as well as developmental emergence of HSPCs (15,17,18). Indeed, many cytokines central to the inflammatory response are also critical to HSPC maintenance and differentiation (19 -21).Extracellular vesicles (EVs) are constitutively released from cells and are powerful paracrine regulator...

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The purpose of the present study was to test the usefulness of dish items selected in developing a dish-based FFQ (DFFQ) to be used for epidemiological studies in Korea. The dietary data of 6817 subjects from the 2001 Korean National Health and Nutrition Examination Survey were used for the analysis. The 24 h recall method was employed for the dietary survey. Initially, ninety-five dish items were selected in developing the DFFQ based on consumption frequency, contribution of selected nutrients and coverage of between-person variations. The usefulness of the selected ninety-five dish items was tested based on their degree of contribution in supplying nutrients in the cumulative percentage contribution (cPC), as well as on their degree of explanation for between-person variation in the cumulative regression coefficient (cMRC). According to the results, the ninety-five selected dish items accounted for an average of 92·3 % of seventeen nutrients consumed by the study subjects based on cPC estimation. The top twenty items among the ninety-five dish items covered 70 to 91 % of the between-person variation for the seventeen nutrients based on cMRC estimation. Thus, the results suggest that the ninety-five items would be useful in developing a FFQ for use in epidemiological studies of Koreans, within less than 10 % underestimation.