The Arf-GEF GBF1 undergoes multi-domain structural shifts to activate Arf at the Golgi.

Golgi homeostasis require the activation of Arf GTPases by the guanine-nucleotide exchange factor requires GBF1, whose recruitment to the Golgi represents a rate limiting step in the process. GBF1 contains a conserved, catalytic, Sec7 domain (Sec7d) and five additional (DCB, HUS, HDS1-3) domains. Herein, we identify the HDS3 domain as essential for GBF1 membrane association in mammalian cells and document the critical role of HDS3 during the development of .

STING protein has a role in lipid metabolism.

Stimulator of interferon genes (STING) plays an important role in innate immunity by controlling type I interferon response against invaded pathogens. In this work, we describe a previously unknown role of STING in lipid metabolism in . Flies with deletion are sensitive to starvation and oxidative stress, have reduced lipid storage, and downregulated expression of lipid metabolism genes.

Humanized Model of the Meier-Gorlin Syndrome Reveals Conserved and Divergent Features of the Orc6 Protein.

Meier-Gorlin syndrome (MGS) is a rare, autosomal recessive disorder characterized by microtia, primordial dwarfism, small ears, and skeletal abnormalities. Patients with MGS often carry mutations in genes encoding the subunits of the Origin Recognition Complex (ORC), components of the prereplicative complex and replication machinery. Orc6 is an important component of ORC and has functions in both DNA replication and cytokinesis.

[Functional Characterization of Septin Complexes].

Septins belong to a family of conserved GTP-binding proteins found in majority of eukaryotic species except for higher plants. Septins form nonpolar complexes that further polymerize into filaments and associate with cell membranes, thus comprising newly acknowledged cytoskeletal system. Septins participate in a variety of cell processes and contribute to various pathophysiological states, including tumorigenesis and neurodegeneration.

Phosphorylation of Pnut in the Early Stages of Embryo Development Affects Association of the Septin Complex with the Membrane and Is Important for Viability.

Septin proteins are polymerizing GTPases that are found in most eukaryotic species. Septins are important for cytokinesis and participate in many processes involving spatial modifications of the cell cortex. In , septin proteins Pnut, Sep1, and Sep2 form a hexameric septin complex.

The Role of Pnut and its Functional Domains in Spermatogenesis.

The Pnut protein belongs to the family of septins, which are conserved GTPases participating in cytokinesis and many more other fundamental cellular processes. Because of their filamentous appearance, membrane association, and functions, septins are considered as the fourth component of the cytoskeleton, along with actin, microtubules, and intermediate filaments. However, septins are much less studied than the other cytoskeleton elements.

[Analysis of Phenotypic Manifestation of peanut Gene Expression Suppression by RNAi in Drosophila Oogenesis].

The gene functions in oogenesis were studied. It was demonstrated that the suppression of expression by RNA interference in follicle cells led to oocyte polarization defects, anomalous cytokinesis in the chorion cells, and aberrant chromatin condensation in follicle cells. No oogenesis abnormalities were observed in females with decreased gene expression in ovarian germline cells.

Drosophila model of Meier-Gorlin syndrome based on the mutation in a conserved C-Terminal domain of Orc6.

Meier-Gorlin syndrome (MGS) is an autosomal recessive disorder characterized by microtia, primordial dwarfism, small ears, and skeletal abnormalities. Patients with MGS often carry mutations in the genes encoding the components of the pre-replicative complex such as Origin Recognition Complex (ORC) subunits Orc1, Orc4, Orc6, and helicase loaders Cdt1 and Cdc6. Orc6 is an important component of ORC and has functions in both DNA replication and cytokinesis.

Endostatin: A novel inhibitor of androgen receptor function in prostate cancer.

Acquired resistance to androgen receptor (AR)-targeted therapies compels the development of novel treatment strategies for castration-resistant prostate cancer (CRPC). Here, we report a profound effect of endostatin on prostate cancer cells by efficient intracellular trafficking, direct interaction with AR, reduction of nuclear AR level, and down-regulation of AR-target gene transcription. Structural modeling followed by functional analyses further revealed that phenylalanine-rich α1-helix in endostatin-which shares structural similarity with noncanonical nuclear receptor box in AR-antagonizes AR transcriptional activity by occupying the activation function (AF)-2 binding interface for coactivators and N-terminal AR AF-1.

Functional insight into the role of Orc6 in septin complex filament formation in Drosophila.

Septins belong to a family of polymerizing GTP-binding proteins that are important for cytokinesis and other processes that involve spatial organization of the cell cortex. We reconstituted a recombinant Drosophila septin complex and compared activities of the wild-type and several mutant septin complex variants both in vitro and in vivo. We show that Drosophila septin complex functions depend on the intact GTP-binding and/or hydrolysis domains of Pnut, Sep1, and Sep2.

A Meier-Gorlin syndrome mutation in a conserved C-terminal helix of Orc6 impedes origin recognition complex formation.

In eukaryotes, DNA replication requires the origin recognition complex (ORC), a six-subunit assembly that promotes replisome formation on chromosomal origins. Despite extant homology between certain subunits, the degree of structural and organizational overlap between budding yeast and metazoan ORC has been unclear. Using 3D electron microscopy, we determined the subunit organization of metazoan ORC, revealing that it adopts a global architecture very similar to the budding yeast complex.

Cyclotron-Bloch dynamics of a quantum particle in a two-dimensional lattice. II. Arbitrary electric field directions.

We study the quantum dynamics of a charged particle in a two-dimensional lattice, subject to constant and homogeneous electric and magnetic fields. We find that different regimes characterize these motions, depending on a combination of conditions, corresponding to weak and strong electric field intensities, rational or irrational directions of the electric field with respect to the lattice, and small or large values of the magnetic (Peierls) phase.

Structural analysis of human Orc6 protein reveals a homology with transcription factor TFIIB.

The Origin Recognition Complex (ORC) is a six-subunit protein important for the initiation of DNA replication in eukaryotic cells. Orc6 is the smallest and the least conserved among ORC subunits. It is required for the DNA replication but also has a function in cytokinesis in metazoan species, however, the mechanisms of Orc6 action in these processes are not clear.

Study of DNA replication in Drosophila using cell free in vitro system.

Using Drosophila early egg extracts we have developed an optimized cell free system to study DNA replication. The efficiency of replication depends on a cold treatment of Drosophila embryos before the extract preparation and a formation of nuclei facilitated by the addition of membrane fractions to the extracts. In vitro DNA replication is ORC and CDC6 dependent, as a removal of these proteins from the extracts abolishes DNA replication.

Functional analysis of an Orc6 mutant in Drosophila.

The origin recognition complex (ORC) is a 6-subunit complex required for the initiation of DNA replication in eukaryotic organisms. ORC is also involved in other cell functions. The smallest Drosophila ORC subunit, Orc6, is important for both DNA replication and cytokinesis.

The origin recognition complex protein family.

Origin recognition complex (ORC) proteins were first discovered as a six-subunit assemblage in budding yeast that promotes the initiation of DNA replication. Orc1-5 appear to be present in all eukaryotes, and include both AAA+ and winged-helix motifs. A sixth protein, Orc6, shows no structural similarity to the other ORC proteins, and is poorly conserved between budding yeast and most other eukaryotic species.

Drosophila Orc6 facilitates GTPase activity and filament formation of the septin complex.

The origin recognition complex or ORC is a six-subunit protein important for DNA replication and other cell functions. Orc6, the smallest subunit of ORC, is essential for both replication and cytokinesis in Drosophila, and interacts with the septin protein Pnut, which is part of the Drosophila septin complex. In this study, we describe the analysis of the interaction of Orc6 with Pnut and whole Drosophila septin complex.

Role of the Orc6 protein in origin recognition complex-dependent DNA binding and replication in Drosophila melanogaster.

The six-subunit origin recognition complex (ORC) is a DNA replication initiator protein in eukaryotes that defines the localization of the origins of replication. We report here that the smallest Drosophila ORC subunit, Orc6, is a DNA binding protein that is necessary for the DNA binding and DNA replication functions of ORC. Orc6 binds DNA fragments containing Drosophila origins of DNA replication and prefers poly(dA) sequences.

Multiple functions of the origin recognition complex.

The origin recognition complex (ORC), a heteromeric six-subunit protein, is a central component for eukaryotic DNA replication. The ORC binds to DNA at replication origin sites in an ATP-dependent manner and serves as a scaffold for the assembly of other key initiation factors. Sequence rules for ORC-DNA binding appear to vary widely.

A cytokinetic function of Drosophila ORC6 protein resides in a domain distinct from its replication activity.

Coordination between separate pathways may be facilitated by the requirements for common protein factors, a finding congruent with the link between proteins regulating DNA replication with other important cellular processes. We report that the smallest of Drosophila origin recognition complex subunits, Orc6, was found in embryos and cell culture localized to the cell membrane and cleavage furrow during cell division as well as in the nucleus. A two-hybrid screen revealed that Orc6 interacts with the Drosophila peanut (pnut), a member of the septin family of proteins important for cell division.

Functional analysis of mutant and wild-type Drosophila origin recognition complex.

The origin recognition complex (ORC) is the DNA replication initiator protein in eukaryotes. We have reconstituted a functional recombinant Drosophila ORC and compared activities of the wild-type and several mutant ORC variants. Drosophila ORC is an ATPase, and our studies show that the ORC1 subunit is essential for ATP hydrolysis and for ATP-dependent DNA binding.

Assembly of functionally active Drosophila origin recognition complex from recombinant proteins.

In eukaryotes the sites for the initiation of chromosomal DNA replication are believed to be determined in part by the binding of a heteromeric origin recognition complex (ORC) to DNA. We have cloned the genes encoding the subunits of the Drosophila ORC. Each of the genes is unique and can be mapped to discrete chromosomal locations implying that the pattern and developmental regulation of origin usage in Drosophila is not regulated solely by a large family of different ORC proteins.

Association of the origin recognition complex with heterochromatin and HP1 in higher eukaryotes.

The origin recognition complex (ORC) is required to initiate eukaryotic DNA replication and also engages in transcriptional silencing in S. cerevisiae. We observed a striking preferential but not exclusive association of Drosophila ORC2 with heterochromatin on interphase and mitotic chromosomes.