Potassium depletion and diastolic dysfunction.
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Adult↗
Biomedical subjects
David B Young
Publications and source records attributed to David B Young.
Identification of domains of ataxia-telangiectasia mutated required for nuclear localization and chromatin association.
Ataxia-telangiectasia mutated (ATM) is essential for rapid induction of cellular responses to DNA double strand breaks (DSBs). In this study, we mapped a nuclear localization signal (NLS), 385KRKK388, within the amino terminus of ATM and demonstrate its recognition by the conventional nuclear import receptor, the importin alpha1/beta1 heterodimer. Although mutation of this NLS resulted in green fluorescent protein (GFP) x ATM(NLSm) localizing predominantly within the cytoplasm, small amounts of nuclear GFP x ATM(NLSm) were still sufficient to elicit a DNA damage response. Insertion of an heterologous nuclear export signal between GFP and ATM(NLSm) resulted in complete cytoplasmic localization of ATM, concomitantly reducing the level of substrate phosphorylation and increasing radiosensitivity, which indicates a functional requirement for ATM nuclear localization. Interestingly, the carboxyl-terminal half of ATM, containing the kinase domain, which localizes to the cytoplasm, could not autophosphorylate itself or phosphorylate substrates, nor could it correct radiosensitivity in response to DSBs even when targeted to the nucleus by insertion of an exogenous NLS, demonstrating that the ATM amino terminus is required for optimal ATM function. Moreover, we have shown that the recruitment/retention of ATM at DSBs requires its kinase activity because a kinase-dead mutant of GFP x ATM failed to form damage-induced foci. Using deletion mutation analysis we mapped a domain in ATM (amino acids 5-224) required for its association with chromatin, which may target ATM to sites of DNA damage. Combined, these data indicate that the amino terminus of ATM is crucial not only for nuclear localization but also for chromatin association, thereby facilitating the kinase activity of ATM in vivo.
Animals↗
Activation of transcription factor NF-kappaB requires ELKS, an IkappaB kinase regulatory subunit.
The nuclear factor-kappa B (NF-kappaB) family of transcription factors plays a seminal role in inflammation, apoptosis, development, and cancer. Modulation of NF-kappaB-mediated gene expression in response to diverse signals is coordinated by the IkappaB kinase (IKK) complex. We identified ELKS, an essential regulatory subunit of the IKK complex. Silencing ELKS expression by RNA interference blocked induced expression of NF-kappaB target genes, including the NF-kappaB inhibitor IkappaBalpha and proinflammatory genes such as cyclo-oxygenase 2 and interleukin 8. These cells were also not protected from apoptosis in response to cytokines. ELKS likely functions by recruiting IkappaBalpha to the IKK complex and thus serves a regulatory function for IKK activation.
Adaptor Proteins, Signal Transducing↗
A novel viral mechanism for dysregulation of beta-catenin in Kaposi's sarcoma-associated herpesvirus latency.
The Kaposi's sarcoma-associated herpesvirus (KSHV) latency-associated nuclear antigen (LANA) is expressed in all KSHV-associated tumors, including Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). We found that beta-catenin is overexpressed in both PEL cells and KS tissue. Introduction of anti-LANA small interfering RNA (siRNA) into PEL cells eliminated beta-catenin accumulation; LANA itself upregulated expression of beta-catenin in transfected cells. LANA stabilizes beta-catenin by binding to the negative regulator GSK-3beta, causing a cell cycle-dependent nuclear accumulation of GSK-3beta. The LANA C terminus contains sequences similar to the GSK-3beta-binding domain of Axin. Disruption of this region resulted in a mutant LANA that failed to re-localize GSK-3beta or stabilize beta-catenin. The importance of this pathway to KSHV-driven cell proliferation was highlighted by the observation that LANA, but not mutant LANA, stimulates entry into S phase. Redistribution of GSK-3beta can therefore be a source of beta-catenin dysregulation in human cancers.
Amino Acid Sequence↗
Fanconi anemia protein complex is a novel target of the IKK signalsome.
Fanconi anemia (FA), a genetic disorder predisposing to aplastic anemia and cancer, is characterized by hypersensitivity to DNA-damaging agents and oxidative stress. Five of the cloned FA proteins (FANCA, FANCC, FANCE, FANCF, FANCG) appear to be involved in a common functional pathway that is required for the monoubiquitination of a sixth gene product, FANCD2. Here, we report that FANCA associates with the IkappaB kinase (IKK) signalsome via interaction with IKK2. Components of the FANCA complex undergo rapid, stimulus-dependent changes in phosphorylation, which are blocked by kinase-inactive IKK2 (IKK2 K > M). When exposed to mitomycin C, cells expressing IKK2 K > M develop a cell cycle abnormality characteristic of FA. Thus, FANCA may function to recruit IKK2, thus providing the cell a means of rapidly responding to stress.
Adenoviridae↗
Ethnicity and unprovoked hypokalemia in the Atherosclerosis Risk in Communities Study.
BACKGROUND: Hypertension is more prevalent in the African American population when compared with the European American population in the United States. Unprovoked hypokalemia may lead to hypertension and is associated with several forms of recognized secondary hypertension. METHODS: We investigated the association of ethnicity with unprovoked hypokalemia in the second Atherosclerosis Risk in Communities (ARIC) study examination. Hypokalemia was defined as serum potassium <3.5 mmol/L. RESULTS: A statistically significant association was detected between ethnicity and unprovoked hypokalemia (odds ratio = 5.3; 95% confidence interval = 3.6, 7.7) with unprovoked hypokalemia more prevalent in African Americans both before and after adjustment for important covariates. The unadjusted prevalence for unprovoked hypokalemia was 2.6% for African Americans and 0.5% for European Americans. CONCLUSIONS: We found that the prevalence of unprovoked hypokalemia for African Americans in the ARIC cohort was more than five times that for European Americans. These data suggest that an increased awareness of hypokalemia and its etiology may be indicated for African Americans.
Arteriosclerosis↗
Protein interactions targeting the latency-associated nuclear antigen of Kaposi's sarcoma-associated herpesvirus to cell chromosomes.
Maintenance of Kaposi's sarcoma-associated herpesvirus (KSHV) latent infection depends on the viral episomes in the nucleus being distributed to daughter cells following cell division. The latency-associated nuclear antigen (LANA) is constitutively expressed in all KSHV-infected cells. LANA binds sequences in the terminal repeat regions of the KSHV genome and tethers the viral episomes to chromosomes. To better understand the mechanism of chromosomal tethering, we performed glutathione S-transferase (GST) affinity and yeast two-hybrid assays to identify LANA-interacting proteins with known chromosomal association. Two of the interactors were the methyl CpG binding protein MeCP2 and the 43-kDa protein DEK. The interactions of MeCP2 and DEK with LANA were confirmed by coimmunoprecipitation. The MeCP2-interacting domain was mapped to the previously described chromatin binding site in the N terminus of LANA, while the DEK-interacting domain mapped to LANA amino acids 986 to 1043 in the C terminus. LANA was unable to associate with mouse chromosomes in chromosome spreads of transfected NIH 3T3 cells. However, LANA was capable of targeting to mouse chromosomes in the presence of human MeCP2 or DEK. The data indicate that LANA is tethered to chromosomes through two independent chromatin binding domains that interact with different protein partners.
Amino Acid Sequence↗