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Summary: MCM proteins are components of a DNA helicase that plays an essential role in DNA replication and cell proliferation. However, MCM proteins are present in excess relative to origins of replication, suggesting they may serve other functions. Decreased proliferation is a fundamental physiological response to hypoxia in many cell types, and hypoxia-inducible factor 1 (HIF-1) has been implicated in this process. Here, we demonstrate that multiple MCM proteins bind directly to the HIF-1α subunit and synergistically inhibit HIF-1 transcriptional activity via distinct O2-dependent mechanisms. MCM3 inhibits transactivation domain function, whereas MCM7 enhances HIF-1α ubiquitination and proteasomal degradation. HIF-1 activity decreases when quiescent cells re-enter the cell cycle, and this effect is MCM dependent. Exposure to hypoxia leads to MCM2–7 downregulation in diverse cell types. These studies reveal a function of MCM proteins apart from their DNA helicase activity and establish a direct link between HIF-1 and the cell-cycle machinery. [Copyright &y& Elsevier]

Summary: The pyruvate kinase isoforms PKM1 and PKM2 are alternatively spliced products of the PKM2 gene. PKM2, but not PKM1, alters glucose metabolism in cancer cells and contributes to tumorigenesis by mechanisms that are not explained by its known biochemical activity. We show that PKM2 gene transcription is activated by hypoxia-inducible factor 1 (HIF-1). PKM2 interacts directly with the HIF-1α subunit and promotes transactivation of HIF-1 target genes by enhancing HIF-1 binding and p300 recruitment to hypoxia response elements, whereas PKM1 fails to regulate HIF-1 activity. Interaction of PKM2 with prolyl hydroxylase 3 (PHD3) enhances PKM2 binding to HIF-1α and PKM2 coactivator function. Mass spectrometry and anti-hydroxyproline antibody assays demonstrate PKM2 hydroxylation on proline-403/408. PHD3 knockdown inhibits PKM2 coactivator function, reduces glucose uptake and lactate production, and increases O2 consumption in cancer cells. Thus, PKM2 participates in a positive feedback loop that promotes HIF-1 transactivation and reprograms glucose metabolism in cancer cells. [ABSTRACT FROM AUTHOR]

TANK-binding kinase 1 (TBK1) is a potential therapeutic target in multiple cancers, including clear cell renal cell carcinoma (ccRCC). However, targeting TBK1 in clinical practice is challenging. One approach to overcome this challenge would be to identify an upstream TBK1 regulator that could be targeted therapeutically in cancer specifically. In this study, we perform a kinome-wide small interfering RNA (siRNA) screen and identify doublecortin-like kinase 2 (DCLK2) as a TBK1 regulator in ccRCC. DCLK2 binds to and directly phosphorylates TBK1 on Ser172. Depletion of DCLK2 inhibits anchorage-independent colony growth and kidney tumorigenesis in orthotopic xenograft models. Conversely, overexpression of DCLK2203, a short isoform that predominates in ccRCC, promotes ccRCC cell growth and tumorigenesis in vivo. Mechanistically, DCLK2203 elicits its oncogenic signaling via TBK1 phosphorylation and activation. Taken together, these results suggest that DCLK2 is a TBK1 activator and potential therapeutic target for ccRCC. [Display omitted] • An unbiased kinome-wide siRNA screen identifies DCLK2 as a TBK1 activator in ccRCC • Depletion of DCLK2 inhibits ccRCC growth both in vitro and in vivo • DCLK2 gene produces multiple isoforms, among which DCLK2203 predominates in ccRCC • DCLK2203 is essential for TBK1 phosphorylation and ccRCC growth in vitro and in vivo Hu et al. discover that a kinase, DCLK2, promotes tumorigenesis in ccRCC by activating TBK1 phosphorylation. The oncogenic role of DCLK2 is mainly elicited by a specific splice isoform. Targeting DCLK2 to selectively inhibit TBK1 activity in cancer cells could emerge as a potential therapeutic strategy in ccRCC. [ABSTRACT FROM AUTHOR]

Summary: T cell differentiation into distinct functional effector and inhibitory subsets is regulated, in part, by the cytokine environment present at the time of antigen recognition. Here, we show that hypoxia-inducible factor 1 (HIF-1), a key metabolic sensor, regulates the balance between regulatory T cell (Treg) and TH17 differentiation. HIF-1 enhances TH17 development through direct transcriptional activation of RORγt and via tertiary complex formation with RORγt and p300 recruitment to the IL-17 promoter, thereby regulating TH17 signature genes. Concurrently, HIF-1 attenuates Treg development by binding Foxp3 and targeting it for proteasomal degradation. Importantly, this regulation occurs under both normoxic and hypoxic conditions. Mice with HIF-1α-deficient T cells are resistant to induction of TH17-dependent experimental autoimmune encephalitis associated with diminished TH17 and increased Treg cells. These findings highlight the importance of metabolic cues in T cell fate determination and suggest that metabolic modulation could ameliorate certain T cell-based immune pathologies. [ABSTRACT FROM AUTHOR]

Regulatory T (Treg) cells suppress inflammatory immune responses and autoimmunity caused by self-reactive T cells. The key Treg cell transcription factor Foxp3 is downregulated during inflammation to allow for the acquisition of effector T cell-like functions. Here, we demonstrate that stress signals elicited by proinflammatory cytokines and lipopolysaccharides lead to the degradation of Foxp3 through the action of the E3 ubiquitin ligase Stub1. Stub1 interacted with Foxp3 to promote its K48-linked polyubiquitination in an Hsp70-dependent manner. Knockdown of endogenous Stub1 or Hsp70 prevented Foxp3 degradation. Furthermore, the overexpression of Stub1 in Treg cells abrogated their ability to suppress inflammatory immune responses in vitro and in vivo and conferred a T-helper-1-cell-like phenotype. Our results demonstrate the critical role of the stress-activated Stub1-Hsp70 complex in promoting Treg cell inactivation, thus providing a potential therapeutic target for the intervention against autoimmune disease, infection, and cancer., (Copyright © 2013 Elsevier Inc. All rights reserved.)

T cell differentiation into distinct functional effector and inhibitory subsets is regulated, in part, by the cytokine environment present at the time of antigen recognition. Here, we show that hypoxia-inducible factor 1 (HIF-1), a key metabolic sensor, regulates the balance between regulatory T cell (T(reg)) and T(H)17 differentiation. HIF-1 enhances T(H)17 development through direct transcriptional activation of RORγt and via tertiary complex formation with RORγt and p300 recruitment to the IL-17 promoter, thereby regulating T(H)17 signature genes. Concurrently, HIF-1 attenuates T(reg) development by binding Foxp3 and targeting it for proteasomal degradation. Importantly, this regulation occurs under both normoxic and hypoxic conditions. Mice with HIF-1α-deficient T cells are resistant to induction of T(H)17-dependent experimental autoimmune encephalitis associated with diminished T(H)17 and increased T(reg) cells. These findings highlight the importance of metabolic cues in T cell fate determination and suggest that metabolic modulation could ameliorate certain T cell-based immune pathologies., (Copyright © 2011 Elsevier Inc. All rights reserved.)