Derepression of Mouse β-Major-Globin Gene Transcription during Erythroid Differentiation

Macleod, Kay F.; Plumb, Mark

doi:10.1128/mcb.11.9.4324-4332.1991

Cited by 4 publications

(1 citation statement)

References 54 publications

(105 reference statements)

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“…KU70 and KU80 make up a heterodimer that is a major enzyme involved in DNA damage repair and the maintenance of telomere length. Mice homozygous for KU70 mutations are very sensitive to ionizing radiation [48], and mice lacking the KU70 or KU80 gene are characterized by premature aging [49]. Therefore, it has been argued that double-strand DNA breaks contribute to aging, and it is known that DNA damage repair is reduced in the AD brain [50].…”

Section: Discussionmentioning

confidence: 99%

Diverse proteins aggregate in mild cognitive impairment and Alzheimer’s disease brain

et al. 2020

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Background All cells accumulate insoluble protein aggregates throughout their lifespan. While many studies have characterized the canonical disease-associated protein aggregates, such as those associated with amyloid plaques, additional, undefined proteins aggregate in the brain and may be directly associated with disease and lifespan. Methods A proteomics approach was used to identify a large subset of insoluble proteins in the mild cognitively impaired (MCI) and Alzheimer’s disease (AD) human brain. Cortical samples from control, MCI, and AD patients were separated into detergent-soluble and detergent-insoluble fractions, and high-resolution LC/MS/MS technology was used to determine which proteins became more insoluble in the disease state. Bioinformatics analyses were used to determine if the alteration of protein aggregation between AD and control patients was associated with any specific biological process. Western blots were used to validate the proteomics data and to assess the levels of secondary protein modifications in MCI and AD. Results There was a stage-dependent increase in detergent-insoluble proteins, with more extreme changes occurring in the AD cohort. Glycolysis was the most significantly overrepresented gene ontology biological process associated with the alteration of protein aggregation between AD and control patients. It was further shown that many low molecular weight proteins that were enriched in the AD brain were also highly aggregated, migrating on SDS-PAGE far above their predicted molecular masses. Glucose-6-phosphate isomerase, ubiquitin carboxyl-terminal hydrolase isoenzyme L1 (UCHL1/PARK5), and the DNA damage repair enzyme KU70 were among the top insoluble proteins identified by proteomics and validated by Western blot to be increased in the insoluble fractions of both MCI and AD brain samples. Conclusions Diverse proteins became more detergent-insoluble in the brains of both MCI and AD patients compared to age-matched controls, suggesting that multiple proteins aggregate in these diseases, likely posing a direct toxic insult to neurons. Furthermore, detergent-insoluble proteins included those with important biological activities for critical cellular processes such as energetics, proteolysis, and DNA damage repair. Thus, reduced protein solubility likely promotes aggregation and limits functionality, reducing the efficiency of multiple aspects of cell physiology. Pharmaceutical interventions that increase autophagy may provide a useful therapeutic treatment to combat protein aggregation.

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Section: Discussionmentioning

confidence: 99%

Diverse proteins aggregate in mild cognitive impairment and Alzheimer’s disease brain

et al. 2020

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Specific repression of β-globin promoter activity by nuclear ferritin

Broyles

Belegu²,

DeWitt³

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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Developmental hemoglobin switching involves sequential globin gene activations and repressions that are incompletely understood. Earlier observations, described herein, led us to hypothesize that nuclear ferritin is a repressor of the adult ␤-globin gene in embryonic erythroid cells. Our data show that a ferritin-family protein in K562 cell nuclear extracts binds specifically to a highly conserved CAGTGC motif in the ␤-globin promoter at ؊153 to ؊148 bp from the cap site, and mutation of the CAGTGC motif reduces binding 20-fold in competition gel-shift assays. Purified human ferritin that is enriched in ferritin-H chains also binds the CAGTGC promoter segment. Expression clones of ferritin-H markedly repress ␤-globin promoter-driven reporter gene expression in cotransfected CV-1 cells in which the ␤-promoter has been stimulated with the transcription activator erythroid Krü ppel-like factor (EKLF). We have constructed chloramphenicol acetyltransferase reporter plasmids containing either a wildtype or mutant ␤-globin promoter for the ؊150 CAGTGC motif and have compared the constructs for susceptibility to repression by ferritin-H in cotransfection assays. We find that stimulation by cotransfected EKLF is retained with the mutant promoter, whereas repression by ferritin-H is lost. Thus, mutation of the ؊150 CAGTGC motif not only markedly reduces in vitro binding of nuclear ferritin but also abrogates the ability of expressed ferritin-H to repress this promoter in our cell transfection assay, providing a strong link between DNA binding and function, and strong support for our proposal that nuclear ferritin-H is a repressor of the human ␤-globin gene. Such a repressor could be helpful in treating sickle cell and other genetic diseases.

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BNIP3 Is an RB/E2F Target Gene Required for Hypoxia-Induced Autophagy

Tracy

Dibling

Knabb

et al. 2007

Molecular and Cellular Biology

343

323

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Hypoxia and nutrient deprivation are environmental stresses governing the survival and adaptation of tumor cells in vivo. We have identified a novel role for the Rb tumor suppressor in protecting against nonapoptotic cell death in the developing mouse fetal liver, in primary mouse embryonic fibroblasts, and in tumor cell lines. Loss of pRb resulted in derepression of BNip3, a hypoxia-inducible member of the Bcl-2 superfamily of cell death regulators. We identified BNIP3 as a direct target of pRB/E2F-mediated transcriptional repression and showed that pRB attenuates the induction of BNIP3 by hypoxia-inducible factor to prevent autophagic cell death. BNIP3 was essential for hypoxia-induced autophagy, and its ability to promote autophagosome formation was enhanced under conditions of nutrient deprivation. Knockdown of BNIP3 reduced cell death, and remaining deaths were necrotic in nature. These studies identify BNIP3 as a key regulator of hypoxia-induced autophagy and suggest a novel role for the RB tumor suppressor in preventing nonapoptotic cell death by limiting the extent of BNIP3 induction in cells.Programmed cell death plays an important role in normal developmental processes and in eliminating potentially pathological cells from the organism, and increased resistance to apoptotic cell death is a hallmark of cancer (13). The role of nonapoptotic cell death, including autophagic cell death and programmed necrosis, in cancer is less clear (24,30,56). Autophagy is a well-conserved mechanism activated in response to nutrient deprivation, and it involves the catabolic degradation of macromolecules and organelles by autophagosomes to regenerate metabolites for energy and growth (24, 30). Excess or prolonged autophagy can lead to autophagic cell death (29,40), whereas inhibition of autophagy appears to promote necrotic cell death (7,12). In contrast to processes of apoptosis or autophagic cell death that have tumor suppressor functions, necrosis promotes tumor progression through induction of inflammatory responses that initiate regenerative proliferation and invasion (50). Thus, the factors determining whether a cell undergoes a specific type of cell death (apoptotic, autophagic, or necrotic) in response to a given stress are significant for understanding the progression of cancer.The RB tumor suppressor functions as a negative regulator of the cell cycle through inhibition of E2F transcription factors (49), but it plays other less well defined roles in promoting cell survival (5). In particular, loss of pRB has been shown to sensitize tumor cells to apoptosis induced by chemotherapeutic agents, and certain viral oncoproteins promote apoptosis through the inactivation of pRB (5). However, pRB previously has not been implicated in the regulation of nonapoptotic cell death.Mice lacking the function of pRb die in midgestation and exhibit various developmental defects, including increased cell death in the nervous system, lens, and liver (5). Although cell death in the lens and peripheral nervous system likely is due t...

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Derepression of Mouse β-Major-Globin Gene Transcription during Erythroid Differentiation

Cited by 4 publications

References 54 publications

Diverse proteins aggregate in mild cognitive impairment and Alzheimer’s disease brain

Diverse proteins aggregate in mild cognitive impairment and Alzheimer’s disease brain

Specific repression of β-globin promoter activity by nuclear ferritin

BNIP3 Is an RB/E2F Target Gene Required for Hypoxia-Induced Autophagy

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