SummaryFully-grown mammalian oocytes maintain a prophase I, germinal-vesicle stage arrest in the ovary for extended periods before a mid-cycle luteinizing surge induces entry into the first meiotic division. Cdh1 is an activator of the Anaphase-Promoting Complex (APC), and APC cdh1 is normally restricted to late M -early G1 of the cell cycle. Here we find that APC cdh1 is active in mouse oocytes and is necessary to maintain prophase arrest.Fully-grown mammalian oocytes remain arrested at prophase I within antral follicles until stimulated to enter the first meiotic division by a mid-cycle surge in luteinising hormone. An oolemma receptor maintains this arrest by raising protein kinase A activity1 which inhibits Maturation-Promoting Factor (CDK1-cyclin B1) by affecting the phosphorylation status of CDK12. Oocytes can resume meiosis spontaneously, manifest by germinal vesicle breakdown (GVB), when released into culture media, but remain arrested if agents such as the phosphodiesterase inhibitor milrinone3, are added to maintain protein kinase A.Raising cyclin B1 levels in milrinone-arrested oocytes by microinjection of its cRNA coupled to GFP induced GVB. Spatially the cyclin B1-GFP expressed in oocytes mirrored the distribution reported in adult cells 4 ( Supplementary Information, Fig S1a). Cytoplasmic cyclin B1 entered the nucleus before GVB and became associated with chromatin afterwards. However, the GVB rate in these oocytes was <15% by 5 h (Fig 1a), and never exceeded 20%, even after 24 h. The proteasomal inhibitor MG132 had a mild stimulatory effect on GVB over 5 h, and when combined with cyclin B1 the rate GVB increased 2-3 fold compared to cyclin B1 alone (Fig 1a and see Supplementary Information, Table S1). The increased rate of GVB was likely caused by increased cyclin B1-GFP since levels doubled with MG132 (Fig 1b).Cyclin B1 degradation requires polyubiquitination by the Anaphase-Promoting Complex (APC) followed by proteasomal degradation5. In mitosis, the APC needs one of two essential co-activators, cdc20 and cdh1, which are both present in mouse eggs6. APC cdc20 and APC cdh1 both degrade substrates such as cyclin B1 that contain a Destruction-(D)-box. Therefore we repeated the above cyclin B1 experiment using Δ90-cyclin B1, an N-terminal truncation which removes the D-box 7. Δ90-cyclin B1 cRNA induced 70% GVB rates by 5 h (Fig 1a), and 80% by 24 h; rates that are 4-5 fold higher than cyclin B1-GFP and with the MG132 data are consistent with cyclin B1 being degraded in GV oocytes.Cyclin B1 degradation in oocytes, where MPF is low, is likely due to APC cdh1 because APC cdc20 requires high MPF levels for activity8. Oocytes do contain cdh1 (see Supplementary Information, Fig S1b) therefore to examine if APC cdh1 was active at this time, in addition to cyclin B1, we coupled two further APC cdh1 substrates to GFP, injected their cRNA and measured their stability following protein synthesis inhibition. We used cdc20 itself and a mutant form of securin (securin dm ) in which its D-Box has been mutated. Bo...

Sentrin/small ubiquitin-like modifier (SUMO) is protein modification pathway that regulates multiple biological processes, including cell division, DNA replication/repair, signal transduction, and cellular metabolism. In this review, we will focus on recent advances in the mechanisms of disease pathogenesis, such as cancer, diabetes, seizure, and heart failure, which have been linked to the SUMO pathway. SUMO is conjugated to lysine residues in target proteins through an isopeptide linkage catalyzed by SUMO-specific activating (E1), conjugating (E2), and ligating (E3) enzymes. In steady state, the quantity of SUMO-modified substrates is usually a small fraction of unmodified substrates due to the deconjugation activity of the family Sentrin/SUMO-specific proteases (SENPs). In contrast to the complexity of the ubiquitination/deubiquitination machinery, the biochemistry of SUMOylation and de-SUMOylation is relatively modest. Specificity of the SUMO pathway is achieved through redox regulation, acetylation, phosphorylation, or other posttranslational protein modification of the SUMOylation and de-SUMOylation enzymes. There are three major SUMOs. SUMO-1 usually modifies a substrate as a monomer; however, SUMO-2/3 can form poly-SUMO chains. The monomeric SUMO-1 or poly-SUMO chains can interact with other proteins through SUMO-interactive motif (SIM). Thus SUMO modification provides a platform to enhance protein-protein interaction. The consequence of SUMOylation includes changes in cellular localization, protein activity, or protein stability. Furthermore, SUMO may join force with ubiquitin to degrade proteins through SUMO-targeted ubiquitin ligases (STUbL). After 20 yr of research, SUMO has been shown to play critical roles in most, if not all, biological pathways. Thus the SUMO enzymes could be targets for drug development to treat human diseases.

Flexible synthesized MoS2 transistors are advanced to perform at GHz speeds. An intrinsic cutoff frequency of 5.6 GHz is achieved and analog circuits are realized. Devices are mechanically robust for 10,000 bending cycles.

Modern cancer therapy has successfully cured many cancers and converted a terminal illness to chronic disease. Because cancer patients often have co-existing heart diseases, expert advice from the cardiologists will improve clinical outcome. In addition, cancer therapy can also cause myocardial damage, induce endothelial dysfunction, and alter cardiac conduction. Thus, it is important for practicing cardiologists to be knowledgeable about the diagnosis, prevention, and management of cardiovascular complications of cancer therapy. In this first part of a 2-part review, we will review cancer therapy-induced cardiomyopathy and ischemia. This review is based on MEDLINE literature search, published clinical guidelines, and best practices in major cancer centers. With the number of cancer survivors expanding quickly, the time has come for cardiologists to work closely with cancer specialists to prevent and treat cancer therapy-induced cardiovascular complications.

SummaryThe first female meiotic division (MI) is uniquely prone to chromosome segregation errors through non-disjunction, resulting in trisomies and early pregnancy loss1. Here, we show a fundamental difference in the control of mammalian meiosis which may underlie such susceptibility. It involved a reversal in the well-established timing of activation of the AnaphasePromoting Complex (APC)2, 3 by its co-activators cdc20 and cdh1. APC cdh1 was active first, during prometaphase I, and was needed in order to allow homologue congression, since loss of cdh1 speeded up MI, leading to premature chromosome segregation and a non-disjunction phenotype. APC cdh1 targeted cdc20 for degradation but not securin and cyclin B1. These were degraded later in MI through APC cdc20 , making cdc20 re-synthesis essential for successful meiotic progression. The switch from APC cdh1 to APC cdc20 activity was controlled by increasing CDK1 and cdh1 loss. These findings demonstrate a fundamentally different mechanism of control for the first meiotic division in mammalian oocytes not observed in meioses of other species.The E3 ligase activity of the Anaphase-Promoting Factor (APC) bound to its co-activator cdh1 (APC cdh1 ) is commonly associated with late M-and early G1-phases of the cell cycle, where it contributes to M-phase exit by degradation of mitotic proteins, while simultaneously preventing precocious DNA replication3-6. APC cdh1 activity is also observed in germinal vesicle stage (GV) mouse oocytes, equivalent to late G2, where it contributes to cyclin B1 degradation and as such is required for maintenance of GV arrest7, 8.We wanted to establish if cdh1 had any role in meiosis I (MI) after GV breakdown (GVB), independent of its role in maintaining GV arrest. Therefore, we examined the ability of oocytes to progress through MI following microinjection with a cdh1 antisense morpholino (cdh1 MO ). Culture in milrinone-containing medium for 24 h following cdh1 MO microinjection is sufficient to reduce cdh1 levels by >90% (hereafter 'cdh1 knockdown oocytes') but maintain GV arrest in the majority of oocytes, with longer term culture (48h) needed to promote GVB7. In cdh1 knockdown oocytes, which maintained arrest over 24 h, we found that progression through MI was accelerated following milrinone wash-out. Oocytes extruded a polar body (PB), which forms on completion of MI, 1.5 h earlier than non-injected oocytes (Fig 1a). This effect was attributed specifically to loss of cdh1, since it Correspondence should be addressed to KTJ. (email: k.t.jones@ncl.ac.uk). AUTHOR CONTRIBUTIONS K.T.J. directed the work. A.R. and S.M. performed most the experiments; with HY.C making the initial observations on the effects of the cdh1 MO , I.N. performing some of the Westerns, and M.L. making some of the constructs. KTJ wrote the paper in consultation with A.R. and S.M. COMPETING FINANCIAL INTERESTSThe authors declare no competing financial interests. was not observed in mock cdh1 depleted oocytes through addition of a 5-base-mismatch cdh1 morpholino (5...