Molecular insights into vesicle tethering at the Golgi by the conserved oligomeric Golgi (COG) complex and the golgin TATA element modulatory factor (TMF).

Protein sorting between eukaryotic compartments requires vesicular transport, wherein tethering provides the first contact between vesicle and target membranes. Here we map and start to functionally analyze the interaction network of the conserved oligomeric Golgi (COG) complex that mediates retrograde tethering at the Golgi. The interactions of COG subunits with members of transport factor families assign the individual subunits as specific interaction hubs. Functional analysis of selected interactions suggests a mechanistic tethering model. We find that the COG complex interacts with two different Rabs in addition to each end of the golgin "TATA element modulatory factor" (TMF). This allows COG to potentially bridge the distance between the distal end of the golgin and the target membrane thereby promoting tighter docking. Concurrently we show that the central portion of TMF can bind to Golgi membranes that are liberated of their COPI cover. This latter interaction could serve to bring vesicle and target membranes into close apposition prior to fusion. A target selection mechanism, in which a hetero-oligomeric tethering factor organizes Rabs and coiled transport factors to enable protein sorting specificity, could be applicable to vesicle targeting throughout eukaryotic cells.

Variant Ciz1 is a circulating biomarker for early-stage lung cancer.

There is an unmet need for circulating biomarkers that can detect early-stage lung cancer. Here we show that a variant form of the nuclear matrix-associated DNA replication factor Ciz1 is present in 34/35 lung tumors but not in adjacent tissue, giving rise to stable protein quantifiable by Western blot in less than a microliter of plasma from lung cancer patients. In two independent sets, with 170 and 160 samples, respectively, variant Ciz1 correctly identified patients who had stage 1 lung cancer with clinically useful accuracy. For set 1, mean variant Ciz1 level in individuals without diagnosed tumors established a threshold that correctly classified 98% of small cell lung cancers (SCLC) and non-SCLC patients [receiver operator characteristic area under the curve (AUC) 0.958]. Within set 2, comparison of patients with stage 1 non-SCLC with asymptomatic age-matched smokers or individuals with benign lung nodules correctly classified 95% of patients (AUCs 0.913 and 0.905), with overall specificity of 76% and 71%, respectively. Moreover, using the mean of controls in set 1, we achieved 95% sensitivity among patients with stage 1 non-SCLC patients in set 2 with 74% specificity, demonstrating the robustness of the classification. RNAi-mediated selective depletion of variant Ciz1 is sufficient to restrain the growth of tumor cells that express it, identifying variant Ciz1 as a functionally relevant driver of cell proliferation in vitro and in vivo. The data show that variant Ciz1 is a strong candidate for a cancer-specific single marker capable of identifying early-stage lung cancer within at-risk groups without resort to invasive procedures.

Phylogeny of the Glomerales and Diversisporales (fungi: Glomeromycota) from actin and elongation factor 1-alpha sequences.

The arbuscular mycorrhizal (AM) fungi have been elevated to the phylum Glomeromycota based on a ribosomal gene phylogeny. In order to test this phylogeny, we amplified and sequenced small subunit ribosomal RNA (SSUrRNA), actin and elongation factor 1 (EF1)-alpha gene fragments from single spores of Acaulospora laevis, Glomus caledonium, Gigaspora margarita, and Scutellospora dipurpurescens. Sequence variation within and among spores of an isolate was low except for SSUrRNA in S. dipurpurescens, and the actin amino acid sequence was more conserved than that of EF1-alpha. The AM fungal sequences were more similar to one another than to any other fungal group. Joint phylogenetic analysis of the actin and EF1-alpha sequences suggested that the sister group to the AM fungi was a Zygomycete order, the Mortierellales.