CDK-dependent nuclear localization of B-Cyclin Clb1 promotes FEAR activation during meiosis I in budding yeast

Cyclin-dependent kinases (CDK) are master regulators of the cell cycle in eukaryotes. CDK activity is regulated by the presence, post-translational modification and spatial localization of its regulatory subunit cyclin. In budding yeast, the B-cyclin Clb1 is phosphorylated and localizes to the nucleus during meiosis I. However the functional significance of Clb1's phosphorylation and nuclear localization and their mutual dependency is unknown. In this paper, we demonstrate that meiosis-specific phosphorylation of Clb1 requires its import to the nucleus but not vice versa. While Clb1 phosphorylation is dependent on activity of both CDK and polo-like kinase Cdc5, its nuclear localization requires CDK but not Cdc5 activity. Furthermore we show that increased nuclear localization of Clb1 during meiosis enhances activation of FEAR (Cdc Fourteen Early Anaphase Release) pathway. We discuss the significance of our results in relation to regulation of exit from meiosis I

The Synaptonemal Complex Protein Zip1 Promotes Bi-Orientation of Centromeres at Meiosis I

In meiosis I, homologous chromosomes become paired and then separate from one another to opposite poles of the spindle. In humans, errors in this process are a leading cause of birth defects, mental retardation, and infertility. In most organisms, crossing-over, or exchange, between the homologous partners provides a link that promotes their proper, bipolar, attachment to the spindle. Attachment of both partners to the same pole can sometimes be corrected during a delay that is triggered by the spindle checkpoint. Studies of non-exchange chromosomes have shown that centromere pairing serves as an alternative to exchange by orienting the centromeres for proper microtubule attachment. Here, we demonstrate a new role for the synaptonemal complex protein Zip1. Zip1 localizes to the centromeres of non-exchange chromosomes in pachytene and mediates centromere pairing and segregation of the partners at meiosis I. Exchange chromosomes were also found to experience Zip1-dependent pairing at their centromeres. Zip1 was found to persist at centromeres, after synaptonemal complex disassembly, remaining there until microtubule attachment. Disruption of this centromere pairing, in spindle checkpoint mutants, randomized the segregation of exchange chromosomes. These results demonstrate that Zip1-mediated pairing of exchange chromosome centromeres promotes an initial, bipolar attachment of microtubules. This activity of Zip1 lessens the load on the spindle checkpoint, greatly reducing the chance that the cell will exit the checkpoint delay with an improperly oriented chromosome pair. Thus exchange, the spindle checkpoint, and centromere pairing are complementary mechanisms that ensure the proper segregation of homologous partners at meiosis I

Breakingtheice: A protocol for a randomised controlled trial of an internet-based intervention addressing amphetamine-type stimulant use

Background: The prevalence of amphetamine-type stimulant use is greater than that of opioids and cocaine combined. Currently, there are no approved pharmacotherapy treatments for amphetamine-type stimulant problems, but some face-to-face psychotherapies are of demonstrated effectiveness. However, most treatment services focus on alcohol or opioid disorders, have limited reach and may not appeal to users of amphetamine-type stimulants. Internet interventions have proven to be effective for some substance use problems but none has specifically targeted users of amphetamine-type stimulants. Design/method: The study will use a randomized controlled trial design to evaluate the effect of an internet intervention for amphetamine-type stimulant problems compared with a waitlist control group. The primary outcome will be assessed as amphetamine-type stimulant use (baseline, 3 and 6 months). Other outcomes measures will include ‘readiness to change’, quality of life, psychological distress (K-10 score), days out of role, poly-drug use, help-seeking intention and help-seeking behavior. The intervention consists of three modules requiring an estimated total completion time of 90 minutes. The content of the modules was adapted from face-to-face clinical techniques based on cognitive behavior therapy and motivation enhancement. The target sample is 160 men and women aged 18 and over who have used amphetamine-type stimulants in the last 3 months. Discussion: To our knowledge this will be the first randomized controlled trial of an internet intervention specifically developed for users of amphetamine-type stimulants. If successful, the intervention will offer greater reach than conventional therapies and may engage clients who do not generally seek treatment from existing service providers

Control of the mitotic exit network during meiosis

The mitotic exit network (MEN) is an essential GTPase signaling pathway that triggers exit from mitosis in budding yeast. We show here that during meiosis, the MEN is dispensable for exit from meiosis I but contributes to the timely exit from meiosis II. Consistent with a role for the MEN during meiosis II, we find that the signaling pathway is active only during meiosis II. Our analysis further shows that MEN signaling is modulated during meiosis in several key ways. Whereas binding of MEN components to spindle pole bodies (SPBs) is necessary for MEN signaling during mitosis, during meiosis MEN signaling occurs off SPBs and does not require the SPB recruitment factor Nud1. Furthermore, unlike during mitosis, MEN signaling is controlled through the regulated interaction between the MEN kinase Dbf20 and its activating subunit Mob1. Our data lead to the conclusion that a pathway essential for vegetative growth is largely dispensable for the specialized meiotic divisions and provide insights into how cell cycle regulatory pathways are modulated to accommodate different modes of cell division.National Institutes of Health (U.S.) (Grant number GM62207)Howard Hughes Medical Institute. Investigato