BackgroundCircular RNAs are a class of endogenous RNAs with various functions in eukaryotic cells. Worthy of note, circular RNAs play a critical role in cancer. Currently, nothing is known about their role in head and neck squamous cell carcinoma (HNSCC). The identification of circular RNAs in HNSCC might become useful for diagnostic and therapeutic strategies in HNSCC.ResultsUsing samples from 115 HNSCC patients, we find that circPVT1 is over-expressed in tumors compared to matched non-tumoral tissues, with particular enrichment in patients with TP53 mutations. circPVT1 up- and down-regulation determine, respectively, an increase and a reduction of the malignant phenotype in HNSCC cell lines. We show that circPVT1 expression is transcriptionally enhanced by the mut-p53/YAP/TEAD complex. circPVT1 acts as an oncogene modulating the expression of miR-497-5p and genes involved in the control of cell proliferation.ConclusionsThis study shows the oncogenic role of circPVT1 in HNSCC, extending current knowledge about the role of circular RNAs in cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-017-1368-y) contains supplementary material, which is available to authorized users.

The integral membrane protein Apq12 is an important nuclear envelope (NE)/endoplasmic reticulum (ER) modulator that cooperates with the nuclear pore complex (NPC) biogenesis factors Brl1 and Brr6. How Apq12 executes these functions is unknown. Here, we identified a short amphipathic α-helix (A α H) in Apq12 that links the two transmembrane domains in the perinuclear space and has liposome-binding properties. Cells expressing an APQ12 ( apq12-ah ) version in which A α H is disrupted show NPC biogenesis and NE integrity defects, without impacting Apq12-ah topology or NE/ER localization. Overexpression of APQ12 but not apq12-ah triggers striking over-proliferation of the outer nuclear membrane (ONM)/ER and promotes accumulation of phosphatidic acid (PA) at the NE. Apq12 and Apq12-ah both associate with NPC biogenesis intermediates and removal of A α H increases both Brl1 levels and the interaction between Brl1 and Brr6. We conclude that the short amphipathic α-helix of Apq12 regulates the function of Brl1 and Brr6 and promotes PA accumulation at the NE possibly during NPC biogenesis.

The spindle pole body (SPB) provides microtubule-organizing functions in yeast and duplicates exactly once per cell cycle. The first step in SPB duplication is the half-bridge to bridge conversion via the antiparallel dimerization of the centrin (Cdc31)-binding protein Sfi1 in anaphase. The bridge, which is anchored to the old SPB on the proximal end, exposes free Sfi1 N-termini (N-Sfi1) at its distal end. These free N-Sfi1 promote in G1 the assembly of the daughter SPB (dSPB) in a yet unclear manner. This study shows that N-Sfi1 including the first three Cdc31 binding sites interacts with the SPB components Spc29 and Spc42, triggering the assembly of the dSPB. Cdc31 binding to N-Sfi1 promotes Spc29 recruitment and is essential for satellite formation. Furthermore, phosphorylation of N-Sfi1 has an inhibitory effect and delays dSPB biogenesis until G1. Taking these data together, we provide an understanding of the initial steps in SPB assembly and describe a new function of Cdc31 in the recruitment of dSPB components.