A screen for genes involved in respiration control and longevity in Schizosaccharomyces pombe

We present results showing that glucose signaling has proaging effects in the yeast Schizosaccharomyces pombe. Deletion of the receptor that senses extracellular glucose (Git3) increases the life span of S. pombe, while constitutive activation of the Gα subunit acting downstream of this receptor (Gpa2) shortens its life span. The latter mutant is also impaired for growth under respiration conditions. We have used this phenotype in a selection strategy to identify genes that when overexpressed can rescue the respiratory defect of constitutively active Gα subunit mutants. Here, we report an extended version of the work we presented at the IABG meeting and the results of this screen. This strategy allowed us to isolate four genes: psp1 + /moc1 + , cka1 + , adh1 + , and rpb10 + . Interestingly, the overexpression of these genes was also capable of increasing the chronological life span of wild-type yeast cells

A cross‐lagged twin study of emotional symptoms, social isolation and peer victimisation from early adolescence to emerging adulthood

Background Emotional symptoms, such as anxiety and depressive symptoms, are common during adolescence, often persist over time, and can precede the emergence of severe anxiety and depressive disorders. Studies suggest that a vicious cycle of reciprocal influences between emotional symptoms and interpersonal difficulties may explain why some adolescents suffer from persisting emotional symptoms. However, the role of different types of interpersonal difficulties, such as social isolation and peer victimisation, in these reciprocal associations is still unclear. In addition, the lack of longitudinal twin studies conducted on emotional symptoms during adolescence means that the genetic and environmental contributions to these relationships during adolescence remain unknown. Methods Participants (N = 15,869) from the Twins Early Development Study completed self-reports of emotional symptoms, social isolation and peer victimisation at 12, 16 and 21 years old. A phenotypic cross-lagged model examined reciprocal associations between variables over time, and a genetic extension of this model examined the aetiology of the relationships between variables at each timepoint. Results First, emotional symptoms were reciprocally and independently associated with both social isolation and peer victimisation over time, indicating that different forms of interpersonal difficulties uniquely contributed to emotional symptoms during adolescence and vice versa. Second, early peer victimisation predicted later emotional symptoms via social isolation in mid-adolescence, indicating that social isolation may constitute an intermediate pathway through which peer victimisation predicts longer-term emotional symptoms. Finally, individual differences in emotional symptoms were mostly accounted for by non-shared environmental factors at each timepoint, and both gene–environment and individual-specific environmental mechanisms were involved in the relationships between emotional symptoms and interpersonal difficulties. Conclusions Our study highlights the necessity to intervene early in adolescence to prevent the escalation of emotional symptoms over time and to consider social isolation and peer victimisation as important risk factors for the long-term persistence of emotional symptoms

A cross-lagged twin study of emotional symptoms, social isolation and peer victimisation from early adolescence to emerging adulthood

Background Emotional symptoms, such as anxiety and depressive symptoms, are common during adolescence, often persist over time, and can precede the emergence of severe anxiety and depressive disorders. Studies suggest that a vicious cycle of reciprocal influences between emotional symptoms and interpersonal difficulties may explain why some adolescents suffer from persisting emotional symptoms. However, the role of different types of interpersonal difficulties, such as social isolation and peer victimisation, in these reciprocal associations is still unclear. In addition, the lack of longitudinal twin studies conducted on emotional symptoms during adolescence means that the genetic and environmental contributions to these relationships during adolescence remain unknown. Methods Participants (N = 15,869) from the Twins Early Development Study completed self-reports of emotional symptoms, social isolation and peer victimisation at 12, 16 and 21 years old. A phenotypic cross-lagged model examined reciprocal associations between variables over time, and a genetic extension of this model examined the aetiology of the relationships between variables at each timepoint. Results First, emotional symptoms were reciprocally and independently associated with both social isolation and peer victimisation over time, indicating that different forms of interpersonal difficulties uniquely contributed to emotional symptoms during adolescence and vice versa. Second, early peer victimisation predicted later emotional symptoms via social isolation in mid-adolescence, indicating that social isolation may constitute an intermediate pathway through which peer victimisation predicts longer-term emotional symptoms. Finally, individual differences in emotional symptoms were mostly accounted for by non-shared environmental factors at each timepoint, and both gene–environment and individual-specific environmental mechanisms were involved in the relationships between emotional symptoms and interpersonal difficulties. Conclusions Our study highlights the necessity to intervene early in adolescence to prevent the escalation of emotional symptoms over time and to consider social isolation and peer victimisation as important risk factors for the long-term persistence of emotional symptoms

Structural and functional characterization of interactions involving the Tfb1 subunit of TFIIH and the NER factor Rad2

The general transcription factor IIH (TFIIH) plays crucial roles in transcription as part of the pre-initiation complex (PIC) and in DNA repair as part of the nucleotide excision repair (NER) machinery. During NER, TFIIH recruits the 3′-endonuclease Rad2 to damaged DNA. In this manuscript, we functionally and structurally characterized the interaction between the Tfb1 subunit of TFIIH and Rad2. We show that deletion of either the PH domain of Tfb1 (Tfb1PH) or several segments of the Rad2 spacer region yield yeast with enhanced sensitivity to UV irradiation. Isothermal titration calorimetry studies demonstrate that two acidic segments of the Rad2 spacer bind to Tfb1PH with nanomolar affinity. Structure determination of a Rad2–Tfb1PH complex indicates that Rad2 binds to TFIIH using a similar motif as TFIIEα uses to bind TFIIH in the PIC. Together, these results provide a mechanistic bridge between the role of TFIIH in transcription and DNA repair

The Schizosaccharomyces pombe Hsp104 Disaggregase Is Unable to Propagate the [PSI+] Prion

The molecular chaperone Hsp104 is a crucial factor in the acquisition of thermotolerance in yeast. Under stress conditions, the disaggregase activity of Hsp104 facilitates the reactivation of misfolded proteins. Hsp104 is also involved in the propagation of fungal prions. For instance, the well-characterized [PSI+] prion of Saccharomyces cerevisiae does not propagate in Δhsp104 cells or in cells overexpressing Hsp104. In this study, we characterized the functional homolog of Hsp104 from Schizosaccharomyces pombe (Sp_Hsp104). As its S. cerevisiae counterpart, Sp_hsp104+ is heat-inducible and required for thermotolerance in S. pombe. Sp_Hsp104 displays low disaggregase activity and cannot propagate the [PSI+] prion in S. cerevisiae. When overexpressed in S. cerevisiae, Sp_Hsp104 confers thermotolerance to Δhsp104 cells and reactivates heat-aggregated proteins. However, overexpression of Sp_Hsp104 does not propagate nor eliminate [PSI+]. Strikingly, [PSI+] was cured by overexpression of a chimeric chaperone bearing the C-terminal domain (CTD) of the S. cerevisiae Hsp104 protein. Our study demonstrates that the ability to untangle aggregated proteins is conserved between the S. pombe and S. cerevisiae Hsp104 homologs, and points to a role of the CTD in the propagation of the S. cerevisiae [PSI+] prion

A cross-lagged twin study of emotional symptoms, social isolation, and peer victimisation from early adolescence to emerging adulthood

Background Emotional symptoms, such as anxiety and depressive symptoms, are common during adolescence, often persist over time, and can precede the emergence of severe anxiety and depressive disorders. Studies suggest that a vicious cycle of reciprocal influences between emotional symptoms and interpersonal difficulties may explain why some adolescents suffer from persisting emotional symptoms. However, the role of different types of interpersonal difficulties, such as social isolation and peer victimisation, in these reciprocal associations is still unclear. In addition, the lack of longitudinal twin studies conducted on emotional symptoms during adolescence means that the genetic and environmental contributions to these relationships during adolescence remain unknown. Methods Participants (N = 15,869) from the Twins Early Development Study completed self-reports of emotional symptoms, social isolation and peer victimisation at 12, 16 and 21 years old. A phenotypic cross-lagged model examined reciprocal associations between variables over time, and a genetic extension of this model examined the aetiology of the relationships between variables at each timepoint. Results First, emotional symptoms were reciprocally and independently associated with both social isolation and peer victimisation over time, indicating that different forms of interpersonal difficulties uniquely contributed to emotional symptoms during adolescence and vice versa. Second, early peer victimisation predicted later emotional symptoms via social isolation in mid-adolescence, indicating that social isolation may constitute an intermediate pathway through which peer victimisation predicts longer-term emotional symptoms. Finally, individual differences in emotional symptoms were mostly accounted for by non-shared environmental factors at each timepoint, and both gene–environment and individual-specific environmental mechanisms were involved in the relationships between emotional symptoms and interpersonal difficulties. Conclusions Our study highlights the necessity to intervene early in adolescence to prevent the escalation of emotional symptoms over time and to consider social isolation and peer victimisation as important risk factors for the long-term persistence of emotional symptoms

The CNK–HYP scaffolding complex promotes RAF activation by enhancing KSR–MEK interaction

Abstract The RAS–MAPK pathway regulates cell proliferation, differentiation and survival, and its dysregulation is associated with cancer development. The pathway minimally comprises the small GTPase RAS and the kinases RAF, MEK and ERK. Activation of RAF by RAS is notoriously intricate and remains only partially understood. There are three RAF isoforms in mammals (ARAF, BRAF and CRAF) and two related pseudokinases (KSR1 and KSR2). RAS-mediated activation of RAF depends on an allosteric mechanism driven by the dimerization of its kinase domain. Recent work on human RAFs showed that MEK binding to KSR1 promotes KSR1–BRAF heterodimerization, which leads to the phosphorylation of free MEK molecules by BRAF. Similar findings were made with the single Drosophila RAF homolog. Here we show that the fly scaffold proteins CNK and HYP stabilize the KSR–MEK interaction, which in turn enhances RAF–KSR heterodimerization and RAF activation. The cryogenic electron microscopy structure of the minimal KSR–MEK–CNK–HYP complex reveals a ring-like arrangement of the CNK–HYP complex allowing CNK to simultaneously engage KSR and MEK, thus stabilizing the binary interaction. Together, these results illuminate how CNK contributes to RAF activation by stimulating the allosteric function of KSR and highlight the diversity of mechanisms impacting RAF dimerization as well as the regulatory potential of the KSR–MEK interaction

Calnexin Is Involved in Apoptosis Induced by Endoplasmic Reticulum Stress in the Fission Yeast

Stress conditions affecting the functions of the endoplasmic reticulum (ER) cause the accumulation of unfolded proteins. ER stress is counteracted by the unfolded-protein response (UPR). However, under prolonged stress the UPR initiates a proapoptotic response. Mounting evidence indicate that the ER chaperone calnexin is involved in apoptosis caused by ER stress. Here, we report that overexpression of calnexin in Schizosaccharomyces pombe induces cell death with apoptosis markers. Cell death was partially dependent on the Ire1p ER-stress transducer. Apoptotic death caused by calnexin overexpression required its transmembrane domain (TM), and involved sequences on either side of the ER membrane. Apoptotic death caused by tunicamycin was dramatically reduced in a strain expressing endogenous levels of calnexin lacking its TM and cytosolic tail. This demonstrates the involvement of calnexin in apoptosis triggered by ER stress. A genetic screen identified the S. pombe homologue of the human antiapoptotic protein HMGB1 as a suppressor of apoptotic death due to calnexin overexpression. Remarkably, overexpression of human calnexin in S. pombe also provoked apoptotic death. Our results argue for the conservation of the role of calnexin in apoptosis triggered by ER stress, and validate S. pombe as a model to elucidate the mechanisms of calnexin-mediated cell death