Macroautophagy is an evolutionarily conserved cellular process involved in the clearance of proteins and organelles. Although the autophagy regulation machinery has been widely studied, the key epigenetic control of autophagy process still remains unknown. Here we report that the methyltransferase EZH2 (enhancer of zeste 2 polycomb repressive complex 2 subunit) epigenetically represses several negative regulators of the MTOR (mechanistic target of rapamycin [serine/threonine kinase]) pathway, such as TSC2, RHOA, DEPTOR, FKBP11, RGS16 and GPI. EZH2 was recruited to these genes promoters via MTA2 (metastasis associated 1 family, member 2), a component of the nucleosome remodeling and histone deacetylase (NuRD) complex. MTA2 was identified as a new chromatin binding protein whose association with chromatin facilitated the subsequent recruitment of EZH2 to silenced targeted genes, especially TSC2. Downregulation of TSC2 (tuberous sclerosis 2) by EZH2 elicited MTOR activation, which in turn modulated subsequent MTOR pathway-related events, including inhibition of autophagy. In human colorectal carcinoma (CRC) tissues, the expression of MTA2 and EZH2 correlated negatively with expression of TSC2, which reveals a novel link among epigenetic regulation, the MTOR pathway, autophagy induction, and tumorigenesis.

Suppressor of variegation 3-9 homolog 1 (SUV39H1), a histone methyltransferase, catalyzes histone 3 lysine 9 trimethylation and is involved in heterochromatin organization and genome stability. However, the mechanism for regulation of the enzymatic activity of SUV39H1 in cancer cells is not yet well known. In this study, we identified SET domain-containing protein 7 (SET7/9), a protein methyltransferase, as a unique regulator of SUV39H1 activity. In response to treatment with adriamycin, a DNA damage inducer, SET7/9 interacted with SUV39H1 in vivo, and a GST pull-down assay confirmed that the chromodomain-containing region of SUV39H1 bound to SET7/9. Western blot using antibodies specific for antimethylated SUV39H1 and mass spectrometry demonstrated that SUV39H1 was specifically methylated at lysines 105 and 123 by SET7/9. Although the half-life and localization of methylated SUV39H1 were not noticeably changed, the methyltransferase activity of SUV39H1 was dramatically down-regulated when SUV39H1 was methylated by SET7/ 9. Consequently, H3K9 trimethylation in the heterochromatin decreased significantly, which, in turn, led to a significant increase in the expression of satellite 2 (Sat2) and α-satellite (α-Sat), indicators of heterochromatin relaxation. Furthermore, a micrococcal nuclease sensitivity assay and an immunofluorescence assay demonstrated that methylation of SUV39H1 facilitated genome instability and ultimately inhibited cell proliferation. Together, our data reveal a unique interplay between SET7/9 and SUV39H1-two histone methyltransferases-that results in heterochromatin relaxation and genome instability in response to DNA damage in cancer cells.histone methylation | nonhistone posttranslational modifications

There are several types of capitulum in the Asteraceae due to different combinations of florets varying in corolla shape and stamen development. Previous studies have shown that the formation of ray florets on a radiate capitulum may be related to the parallel co-option of CYC2-like genes among independent Asteraceae lineages. The present work tests that hypothesis and attempts to shed light on the pattern of evolution of the Asteraceae capitulum and floral heteromorphism under the regulation of CYC2-like genes. In this study, the evolutionary history of CYC2-like genes in the Asterales was reconstructed and their expression patterns were examined in species representing different capitulum types and several major Asteraceae lineages. To clarify the role of CYC2d clade genes in morphogenesis of ray flowers, overexpression of ClCYC2d was conducted in Chrysanthemum lavandulifolium. Our results show that there are six CYC2-like members in the Asteraceae; they are results of five duplication events starting from a single-copy gene in the common ancestor of the Goodeniaceae-Calyceraceae-Asteraceae group and completing before the divergence of the subfamily Carduoideae of Asteraceae. Spatial expression pattern of each of the Asteraceae CYC2-like members is conserved across the family. All the six members contribute to the development of the complexity of a capitulum: To form a ray floret, either CYC2c or CYC2g plays an essential role, while CYC2d represses the development of dorsal corolla lobes and stamens of the floret. In sum, the developmental program of making a ray flower is conserved involving functionally divergent CYC2-like genes. Based on extensive species sampling, this study provides an overview of the mode of regulation of CYC2-like genes that patterns the capitulum architectures and their transitions.

Low Reynolds number flow over rectangular cavities is analyzed. The problem is posed to simulate towing tank experiments of Taneda [J. Phys. Soc. Jpn. 46, 1935 (1979)]. A very good agreement exists between numerical and experimental results. The dividing streamline separates from the cavity side wall below the upper corner. The separation point moves toward this corner when the aspect ratio decreases. Flow structure inside the cavity changes considerably with the aspect ratio. Only corner vortices exist in a cavity of aspect ratio W/h=4.0. A decrease of the aspect ratio leads to the enlargement and eventual merger of these vortices. The merger begins with the formation of a stagnation point separating two vortex centers inside the cavity. These vortex centers become progressively weaker and merge to form a single central vortex in a cavity of aspect ratio W/h=2.0. Further decrease of the aspect ratio results in the enlargement of the new corner vortices and their eventual merger. This process begins in a cavity of aspect ratio between 0.6 and 0.575 and is finished in a cavity of aspect ratio 0.5, where two central vortices have been identified. The further decrease of the aspect ratio leads to the sequential repetition of this process and creation of additional central vortices.

The ataxia-telangiectasia mutated (ATM) protein is a key signaling molecule that modulates the DNA damage response. However, the exact mechanism by which ATM regulates DNA damage repair has not yet been elucidated. Here, we report that ATM regulates the DNA damage response by phosphorylating lysine-specific demethylase 2A (KDM2A), a histone demethylase that acts at sites of H3K36 dimethylation. ATM interacts with KDM2A, and their interaction significantly increases in response to DNA double-stranded, but not single-stranded, breaks. ATM specifically phosphorylates KDM2A at threonine 632 (T632) following DNA damage, as demonstrated by a mutagenesis assay and mass spectrometric analysis. Although KDM2A phosphorylation does not alter its own demethylase activity, T632 phosphorylation of KDM2A largely abrogates its chromatin-binding capacity, and H3K36 dimethylation near DNA damage sites is significantly increased. Consequently, enriched H3K36 dimethylation serves as a platform to recruit the MRE11 complex to DNA damage sites by directly interacting with the BRCT2 domain of NBS1, which results in efficient DNA damage repair and enhanced cell survival. Collectively, our study reveals a novel mechanism for ATM in connecting histone modifications with the DNA damage response.