Background: The recent discoveries of microRNA (miRNA) genes and characterization of the first few target genes regulated by miRNAs in Caenorhabditis elegans and Drosophila melanogaster have set the stage for elucidation of a novel network of regulatory control. We present a computational method for wholegenome prediction of miRNA target genes. The method is validated using known examples. For each miRNA, target genes are selected on the basis of three properties: sequence complementarity using a position-weighted local alignment algorithm, free energies of RNA-RNA duplexes, and conservation of target sites in related genomes. Application to the D. melanogaster, Drosophila pseudoobscura and Anopheles gambiae genomes identifies several hundred target genes potentially regulated by one or more known miRNAs.

/pdf/microrna-targets-in-drosophila-51ilqbrm67.pdf

MicroRNA targets in Drosophila

Histones are characterized by numerous posttranslational modifications that influence gene transcription. However, because of the lack of global distribution data in higher eukaryotic systems, the extent to which gene-specific combinatorial patterns of histone modifications exist remains to be determined. Here, we report the patterns derived from the analysis of 39 histone modifications in human CD4(+) T cells. Our data indicate that a large number of patterns are associated with promoters and enhancers. In particular, we identify a common modification module consisting of 17 modifications detected at 3,286 promoters. These modifications tend to colocalize in the genome and correlate with each other at an individual nucleosome level. Genes associated with this module tend to have higher expression, and addition of more modifications to this module is associated with further increased expression. Our data suggest that these histone modifications may act cooperatively to prepare chromatin for transcriptional activation.

/pdf/combinatorial-patterns-of-histone-acetylations-and-3tprg69q8k.pdf

Combinatorial patterns of histone acetylations and methylations in the human genome

BACKGROUND The genetic alterations responsible for an adverse outcome in most patients with acute myeloid leukemia (AML) are unknown. METHODS Using massively parallel DNA sequencing, we identified a somatic mutation in DNMT3A, encoding a DNA methyltransferase, in the genome of cells from a patient with AML with a normal karyotype. We sequenced the exons of DNMT3A in 280 additional patients with de novo AML to define recurring mutations. RESULTS A total of 62 of 281 patients (22.1%) had mutations in DNMT3A that were predicted to affect translation. We identified 18 different missense mutations, the most common of which was predicted to affect amino acid R882 (in 37 patients). We also identified six frameshift, six nonsense, and three splice-site mutations and a 1.5-Mbp deletion encompassing DNMT3A. These mutations were highly enriched in the group of patients with an intermediate-risk cytogenetic profile (56 of 166 patients, or 33.7%) but were absent in all 79 patients with a favorable-risk cytogenetic profile (P<0.001 for both comparisons). The median overall survival among patients with DNMT3A mutations was significantly shorter than that among patients without such mutations (12.3 months vs. 41.1 months, P<0.001). DNMT3A mutations were associated with adverse outcomes among patients with an intermediate-risk cytogenetic profile or FLT3 mutations, regardless of age, and were independently associated with a poor outcome in Cox proportional-hazards analysis. CONCLUSIONS DNMT3A mutations are highly recurrent in patients with de novo AML with an intermediate-risk cytogenetic profile and are independently associated with a poor outcome. (Funded by the National Institutes of Health and others.).

/pdf/dnmt3a-mutations-in-acute-myeloid-leukemia-abrwv1lten.pdf

DNMT3A Mutations in Acute Myeloid Leukemia

Hypertension 66 (20.3%) 24 (24.2%) 30 (16.3%) NS Diabetes 20 (6.2%) 7 (7.1%) 10 (5.4%) NS Excess weight 78 (24%) 27 (27.3%) 44 (23.9%) NS Smokers 64 (19.7%) 17 (17.2%) 35 (19.0%) NS Age >50 years 137 (42.2%) 54 (54.5%) 67 (36.4%) <0.02 Kidney disease 7 (2.2%) 1 (1%) 5 (2.7%) NS Family history, DM 102 (31.4%) 28 (28.3%) 66 (35.9%) NS

Conflict of interest statement. None declared.

Autophagy plays a key role in the maintenance of cellular homeostasis. In healthy cells, such a homeostatic activity constitutes a robust barrier against malignant transformation. Accordingly, many oncoproteins inhibit, and several oncosuppressor proteins promote, autophagy. Moreover, autophagy is required for optimal anticancer immunosurveillance. In neoplastic cells, however, autophagic responses constitute a means to cope with intracellular and environmental stress, thus favoring tumor progression. This implies that at least in some cases, oncogenesis proceeds along with a temporary inhibition of autophagy or a gain of molecular functions that antagonize its oncosuppressive activity. Here, we discuss the differential impact of autophagy on distinct phases of tumorigenesis and the implications of this concept for the use of autophagy modulators in cancer therapy.

https://www.embopress.org/doi/pdf/10.15252/embj.201490784

Autophagy in malignant transformation and cancer progression

Autophagy and Metabolism

The immunodeficiency, centromeric region instability, and facial anomalies syndrome (ICF) is the only disease known to result from a mutated DNA methyltransferase gene, namely, DNMT3B. Characteristic of this recessive disease are decreases in serum immunoglobulins despite the presence of B cells and, in the juxtacentromeric heterochromatin of chromosomes 1 and 16, chromatin decondensation, distinctive rearrangements, and satellite DNA hypomethylation. Although DNMT3B is involved in specific associations with histone deacetylases, HP1, other DNMTs, chromatin remodelling proteins, condensin, and other nuclear proteins, it is probably the partial loss of catalytic activity that is responsible for the disease. In microarray experiments and real-time RT-PCR assays, we observed significant differences in RNA levels from ICF vs. control lymphoblasts for pro- and anti-apoptotic genes (BCL2L10, CASP1, and PTPN13); nitrous oxide, carbon monoxide, NF-κB, and TNFa signalling pathway genes (PRKCH, GUCY1A3, GUCY1B3, MAPK13; HMOX1, and MAP4K4); and transcription control genes (NR2F2 and SMARCA2). This gene dysregulation could contribute to the immunodeficiency and other symptoms of ICF and might result from the limited losses of DNA methylation although ICF-related promoter hypomethylation was not observed for six of the above examined genes. We propose that hypomethylation of satellite 2at1qh and 16qh might provoke this dysregulation gene expression by trans effects from altered sequestration of transcription factors, changes in nuclear architecture, or expression of noncoding RNAs.

https://www.tandfonline.com/doi/pdf/10.1080/08916930802024202

ICF, An Immunodeficiency Syndrome: DNA Methyltransferase 3B Involvement, Chromosome Anomalies, and Gene Dysregulation

Aging constitutes a significant risk factor for fibrosis, and idiopathic pulmonary fibrosis (IPF) is characteristically associated with advancing age. We propose that age-dependent defects in the quality of protein and cellular organelle catabolism may be causally related to pulmonary fibrosis. Our research found that autophagy diminished with corresponding elevated levels of oxidized proteins and lipofuscin in response to lung injury in old mice and middle-aged mice compared to younger animals. More importantly, older mice expose to lung injury are characterized by deficient autophagic response and reduced selective targeting of mitochondria for autophagy (mitophagy). Fibroblast to myofibroblast differentiation (FMD) is an important feature of pulmonary fibrosis in which the profibrotic cytokine TGFβ1 plays a pivotal role. Promotion of autophagy is necessary and sufficient to maintain normal lung fibroblasts’ fate. On the contrary, FMD mediated by TGFβ1 is characterized by reduced autophagy flux, altered mitophagy, and defects in mitochondrial function. In accord with these findings, PINK1 expression appeared to be reduced in fibrotic lung tissue from bleomycin and a TGFβ1-adenoviral model of lung fibrosis. PINK1 expression is also reduced in the aging murine lung and biopsies from IPF patients compared to controls. Furthermore, deficient PINK1 promotes a profibrotic environment. Collectively, this study indicates that an age-related decline in autophagy and mitophagy responses to lung injury may contribute to the promotion and/or perpetuation of pulmonary fibrosis. We propose that promotion of autophagy and mitochondrial quality control may offer an intervention against age-related fibrotic diseases.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/acel.12357

Deregulation of selective autophagy during aging and pulmonary fibrosis: the role of TGFβ1

Kruppel-related zinc finger proteins constitute the largest single class of transcription factors within the human genome. Members of this protein family have the ability to either activate or repress transcription depending on the presence of specific activator or repressor domains within the protein. Approximately one third of the Kruppel-related zinc finger proteins contain an evolutionarily well-conserved repressor domain termed the KRAB domain. This domain acts as a potent repressor of transcription by interacting with the co-repressor protein, TIF1β. TIF1β then, in turn, recruits HP1 proteins, HDACs and probably other proteins involved in gene silencing. In order to identify novel KRAB-containing zinc finger proteins, one mouse monocytic cDNA library and two testis cDNA libraries were screened for novel members of this multigene family. Six novel KRAB-ZNF cDNAs, four mouse and two human, were isolated. The corresponding proteins were all shown to contain N-terminally located KRAB domains as well as varying numbers of C-terminally located zinc finger motifs. An extensive comparative sequence analysis of the KRAB domains of these proteins together with KRAB domains from a large number of previously identified KRAB-ZNF proteins resulted in a clear subdivision into three different subfamilies, A+B, A+b and A. Later, we also isolated a fourth KRAB box, which is present downstream of the KRAB A box in a few proteins of the KRAB A family. This module was named KRAB C. Potential functional differences between these different subfamilies were investigated. In line with previous observations, the KRAB A box was shown to repress transcription, an activity which was enhanced by the presence of the KRAB B box. However, addition of neither the KRAB b box nor the KRAB C box had any effect on repression. Moreover, all KRAB A motifs had the ability to bind TIF1β, and this binding was increased both by the presence of the KRAB B box and by the KRAB C box. The KRAB b box, however, did not seem to contribute to TIF1β-binding. One of the novel human cDNAs, HKr19, was found to be a member of the large ZNF91 family of KRAB zinc finger genes. Interestingly, the expression of HKr19 and a number of other closely related genes were restricted to lymphoid cells, indicating that these genes may be involved in regulating lineage commitment. The effect of HKr19 on cell viability was investigated by transfection into human embryonic kidney cells (HEK 293). The results indicated that HKr19, or its zinc finger domain in isolation, were toxic to these cells when expressed at high levels. The MZF6D protein, on the other hand, showed a testis-specific expression. In situ hybridization analysis located this expression to meiotic germ cells, suggesting a role for this protein in spermatogenesis. Further, the evolutionary perspectives of this large gene family were addressed, and its enormous expansion throughout evolution probably includes numerous duplication events. The results from two extensive sequence analyses give clues to how the repetitive nature of the ZNF motif has given rise to both internal duplications of single motifs as well as duplications of entire genes resulting in gene clusters.

Conserved Interaction Between Distinct Krüppel-associated box Domains and the Transcriptional Intermediary factor 1β

Recent studies have implicated multipotential mesenchymal stem cells (MSCs) as an aid to breast cancer cell proliferation and metastasis, partly as a result of the MSCs secretome. As the tumor gets beyond 2 mm in diameter, the stromal cells could undergo starvation due to the lack of sufficient nutrients in solid tumor microenvironment. In this study, we investigated the survival mechanisms used by stressed stromal cells in breast cancers. We used serum-deprived mesenchymal stem cells (SD-MSCs) and MCF-7 breast cancer cells as model system with a hypothesis that stromal cells in the nutrient-deprived core utilize survival mechanisms for supporting surrounding cells. We tested this hypothesis using in vivo tumor xenografts in immunodeficient mice, which indicated that SD-MSCs supported MCF-7 tumor growth by protection from apoptosis. Histochemical assays showed that SD-MSCs-injected tumors exhibited higher cellularity, decreased apoptosis and decreased differentiation. Beclin-1 staining indicated autophagic areas surrounded by actively proliferating cells. Furthermore, in vitro studies demonstrate that SD-MSCs survive using autophagy and secrete paracrine factors that support tumor cells following nutrient/serum deprivation. Western blot and immunocytochemistry analysis of SD-MSCs demonstrated upregulation and perinuclear relocation of autophagy key regulators such as beclin-1, ATG10, ATG12, MAP-LC3 and lysosomes. Electron microscopic analysis detected a time-dependent increase in autophagosome formation and HDAC6 activity assays indicated the upregulation of autophagy. Taken together, these data suggest that under nutrient-deprived conditions that can occur in solid tumors, stromal cells utilize autophagy for survival and also secrete anti-apoptotic factors that can facilitate solid tumor survival and growth.

/pdf/activation-of-autophagy-in-mesenchymal-stem-cells-provides-g1ifftp0us.pdf

Cecilia G. Sanchez

Papers

Autophagy and Metabolism

ICF, An Immunodeficiency Syndrome: DNA Methyltransferase 3B Involvement, Chromosome Anomalies, and Gene Dysregulation

Deregulation of selective autophagy during aging and pulmonary fibrosis: the role of TGFβ1

Conserved Interaction Between Distinct Krüppel-associated box Domains and the Transcriptional Intermediary factor 1β

Activation of autophagy in mesenchymal stem cells provides tumor stromal support.