Biomedical subjects

B Andrews

Publications and source records attributed to B Andrews.

At least 37 records · Page 2Linked to original sources

PubMed2000

Interactions between Pho85 cyclin-dependent kinase complexes and the Swi5 transcription factor in budding yeast.

Pho85 is a cyclin-dependent protein kinase (Cdk) in budding yeast with roles in cell metabolism and cell cycle progression. Activation of Pho85 occurs through association with Pho85 cyclins (Pcls), of which 10 are known. When complexed with the G1 cyclins, Pcl1 and Pcl2, Pho85 is required for cell cycle progression in the absence of the Cdc28-dependent cyclins, Cln1 and Cln2. To identify potential targets of Pcl2-Pho85, we performed a two-hybrid screen using the Pcl2 cyclin as bait and recovered the transcription factor Swi5 as a Pcl2-interacting protein. We performed both biochemical and genetic tests to discover the biological significance of the interaction between Pcl2 and Swi5 seen in the two-hybrid assay. We found that Swi5 interacts in vitro with Pho85 cyclins and is phosphorylated in vitro by the Pho80-Pho85 kinase. We discovered that a subset of genes that are controlled by Swi5 and a homologous transcription factor, Ace2, was misregulated in a pho85 deletion strain; expression of the ASH1 and CTS1 genes was reduced in an ace2 deletion strain, whereas expression of both genes was increased in an ace2Delta pho85Delta double mutant. We also found that overexpression of SWI5 caused cell lethality in a pho85 deletion strain. Our results are consistent with misregulation of Swi5 activity in vivo in the absence of Pho85 and implicate Swi5 as a potential substrate of Pho85 cyclin-dependent kinase complexes.

Cell Cycle Proteins↗

PubMed2000

A yeast taf17 mutant requires the Swi6 transcriptional activator for viability and shows defects in cell cycle-regulated transcription.

In Saccharomyces cerevisiae, the Swi6 protein is a component of two transcription factors, SBF and MBF, that promote expression of a large group of genes in the late G1 phase of the cell cycle. Although SBF is required for cell viability, SWI6 is not an essential gene. We performed a synthetic lethal screen to identify genes required for viability in the absence of SWI6 and identified 10 complementation groups of swi6-dependent lethal mutants, designated SLM1 through SLM10. We were most interested in mutants showing a cell cycle arrest phenotype; both slm7-1 swi6Delta and slm8-1 swi6Delta double mutants accumulated as large, unbudded cells with increased 1N DNA content and showed a temperature-sensitive growth arrest in the presence of Swi6. Analysis of the transcript levels of cell cycle-regulated genes in slm7-1 SWI6 mutant strains at the permissive temperature revealed defects in regulation of a subset of cyclin-encoding genes. Complementation and allelism tests showed that SLM7 is allelic with the TAF17 gene, which encodes a histone-like component of the general transcription factor TFIID and the SAGA histone acetyltransferase complex. Sequencing showed that the slm7-1 allele of TAF17 is predicted to encode a version of Taf17 that is truncated within a highly conserved region. The cell cycle and transcriptional defects caused by taf17(slm7-1) are consistent with the role of TAF(II)s as modulators of transcriptional activation and may reflect a role for TAF17 in regulating activation by SBF and MBF.

Amino Acid Sequence↗

PubMed2000

Comparison of the effect on bronchial hyperresponsiveness of beclomethasone dipropionate administered via a novel multidose dry-powder inhaler or a conventional pressurised metered dose inhaler.

BACKGROUND: Treatment with inhaled corticosteroids improves symptoms and reduces bronchial hyperresponsiveness (BHR) associated with asthma. Delivery of drugs into the lung is dependent on the inhaler device. Furthermore, environmental concerns regarding the use of chlorofluorocarbon propellants in pressurised inhalers and patient acceptability of inhaler devices both influence the extent of use of different delivery systems. OBJECTIVES: To compare the efficacy of beclomethasone dipropionate (BDP) administered via a novel multidose dry-powder inhaler (DPI) and a conventional pressurised metered-dose inhaler (pMDI) with spacer in patients with BHR. METHODS: A randomised, double-blind, crossover study was carried out in a group of 27 patients (aged 19-55 years) with a clinical diagnosis of reversible airway disease, who demonstrated BHR to methacholine (PD(20) < or =6.4 mg). Each patient received BDP (< or =2 mg/day) via the DPI or pMDI, for periods of 4 weeks. The randomised treatment periods were preceded by 3-week washout periods when no corticosteroid was used. Five clinic visits marked the start and end of each study phase. The primary efficacy endpoint was BHR as defined by the pharmacodynamic parameter, PD(20), which was determined at the start and end of each treatment period. Clinical endpoints including lung function, symptoms and adverse events were also evaluated. RESULTS: Both treatments caused a significant decrease in BHR (p<0.05 vs. pre-treatment values). Mean +/- SD changes in log PD(20) were: DPI 0.59+/-1.29; pMDI 0.59+/-0.94 mg. There was no statistically significant difference between treatments and no evidence of a carry-over effect between treatments on BHR. Clinical efficacy and safety parameters also demonstrated no statistically significant treatment differences, and patients found the DPI easier to use. CONCLUSION: Efficacy of BDP in reducing BHR is comparable via the DPI and pMDI plus spacer.

Administration, Inhalation↗

PubMed2000

The timing, triggers and qualities of recovered memories in therapy.

OBJECTIVES: To report descriptive data on memory recovery of traumatic material including: degree of prior amnesia, triggers to recovery, qualities of the memory and length of time taken to recover different types of memory. DESIGN: British Psychological Society practitioners who reported having clients with recovered memories in a previous large-scale survey were contacted for an indepth interview. They each provided information on up to three such clients. METHODS: From telephone interviews with 108 therapists, we elicited 236 detailed accounts of clients recovering a traumatic memory. Interviews were semistructured with investigator-based ratings. RESULTS: The degree of amnesia varied widely according to therapists: some clients had prior total amnesia, others a prior vague sense or suspicion, and others prior partial memories. Time in therapy before first recall was longer for memories involving child sexual abuse than for memories of other traumas. The majority of the memories, but not all, were similar to those reported by patients with post-traumatic stress disorder: they were fragmented, accompanied by high levels of emotion, and experienced as a reliving of the original event. CONCLUSIONS: On the basis of current understanding of memory processes, several mechanisms may be needed to explain all the data, including disruptions to the encoding and retrieval of traumatic events and errors in the attribution of the source of specific memories. It will be important to confirm these findings by interviewing clients themselves.

Adult↗

PubMed2000

The developmental sequelae of nonorganic failure to thrive.

The developmental sequelae of infant failure to thrive (FTT) were examined in an unreferred group of 6-year-olds with a history of severe nonorganic growth retardation, sampled from a 1-year birth cohort in an inner-city area of South London. Children who failed to thrive in infancy (weight below the third centile for at least 3 months) and their pairwise matched comparisons were originally studied at 15 months, and 42 cases and 42 controls (89.5% of the sample) were followed up. At 6 years, previously growth-retarded children were considerably smaller than matched comparisons, in terms of body mass index (BMI), and height and weight for age Z scores. History of FTT explained substantial variance in weight and BMI at 6 years, with maternal height also contributing to variation in height for age. Child cognitive functioning at 6 years was examined using the McCarthy Scales: cases had more limited quantitative and memory skills than comparisons, but there was no intergroup variation in general cognitive performance. In contrast to analyses of physical development, failure to thrive did not account for cognitive functioning; maternal IQ was the sole significant predictor of performance on all indices of child cognitive abilities. At 15 months, earlier growth faltering was linked to limitations in mental development, but these findings were not confirmed by the follow-up data: the timing of FTT was not related to cognitive abilities at 6 years. Results correspond to past research indicating that nonorganic failure to thrive is associated with persistent limitations in physical stature. There was little evidence of cognitive disadvantage for case group children at school age, suggesting that the adverse effects of early malnutrition on cognitive functioning appear to diminish over time.

Age Factors↗

PubMed1999

Mammalian Cdk5 is a functional homologue of the budding yeast Pho85 cyclin-dependent protein kinase.

Mammalian Cdk5 is a member of the cyclin-dependent kinase family that is activated by a neuron-specific regulator, p35, to regulate neuronal migration and neurite outgrowth. p35/Cdk5 kinase colocalizes with and regulates the activity of the Pak1 kinase in neuronal growth cones and likely impacts on actin cytoskeletal dynamics through Pak1. Here, we describe a functional homologue of Cdk5 in budding yeast, Pho85. Like Cdk5, Pho85 has been implicated in actin cytoskeleton regulation through phosphorylation of an actin-regulatory protein. Overexpression of CDK5 in yeast cells complemented most phenotypes associated with pho85Delta, including defects in the repression of acid phosphatase expression, sensitivity to salt, and a G(1) progression defect. Consistent with the functional complementation, Cdk5 associated with and was activated by the Pho85 cyclins Pho80 and Pcl2 in yeast cells. In a reciprocal series of experiments, we found that Pho85 associated with the Cdk5 activators p35 and p25 to form an active kinase complex in mammalian and insect cells, supporting our hypothesis that Pho85 and Cdk5 are functionally related. Our results suggest the existence of a functionally conserved pathway involving Cdks and actin-regulatory proteins that promotes reorganization of the actin cytoskeleton in response to regulatory signals.

Actins↗

PubMed1999

High-dose versus low-dose D-penicillamine in early diffuse systemic sclerosis: analysis of a two-year, double-blind, randomized, controlled clinical trial.

OBJECTIVE: To test the hypothesis that systemic sclerosis (SSc) patients taking high-dose D-penicillamine (D-Pen) would have greater softening of skin, lower frequency of renal crisis, and better survival than patients taking low-dose D-Pen. METHODS: Seventeen centers enrolled 134 SSc patients with early (< or =18 months) diffuse cutaneous scleroderma into a 2-year, double-blind, randomized comparison of high-dose D-Pen (750-1,000 mg/day) versus low-dose D-Pen (125 mg every other day). All 134 patients were followed up for a mean+/-SD of 4.0+/-1.1 years to assess the frequencies of new-onset scleroderma renal crisis (SRC) and mortality. RESULTS: Sixty-eight patients completed 24 months of drug treatment. The course of the modified Rodnan skin thickness score in the 32 high-dose and the 36 low-dose D-Pen completers was not different at 24 months: the skin score dropped 4.8+/-10.3 (mean+/-SD) units in the high-dose group and 6.9+/-8.4 units in the low-dose group (P = 0.384 by t-test; favoring low-dose D-Pen) from 20.4+/-10.3 in the high-dose and 19.9+/-6.6 in the low-dose D-Pen group at study entry. The incidences of SRC and mortality were not different (P > 0.38 by Cox proportional hazards and by chi-square test) in the 66 high-dose patients (8 developed SRC and 8 died) compared with the 68 low-dose patients (10 developed SRC and 12 died). Of the 20 adverse event-related withdrawals, 80% occurred in the high-dose D-Pen group. CONCLUSION: The course of the skin score and the frequencies of SRC and mortality in the high-dose D-Pen group were not different from those in the low-dose D-Pen group. Eighty percent of the adverse event-related withdrawals occurred in the high-dose D-Pen patients. Although this study cannot answer the question of whether low-dose D-Pen is effective, it does suggest that there is no advantage to using D-Pen in doses higher than 125 every other day.

Adult↗

PubMed1999

Correlates of the disability index of the health assessment questionnaire: a measure of functional impairment in systemic sclerosis.

OBJECTIVE: To evaluate functional impairment in systemic sclerosis (SSc) patients with diffuse cutaneous scleroderma at the time of entry into a trial of a therapeutic intervention (D-penicillamine). METHODS: The 20-item Disability Index of the Health Assessment Questionnaire (HAQ-DI) was administered to 134 patients as they entered a multicenter trial of high-dose versus low-dose D-penicillamine. All patients had diffuse SSc of < 18 months' duration. SSc patients who had severe organ system involvement and recent renal crisis and who were receiving prednisone > 10 mg/day were excluded from entry. Logistic regression modeling was used to examine the relationship of HAQ-DI scores to SSc skin and organ system involvement. Odds ratios (OR) and 95% confidence intervals (95% CI) were used to estimate effects. RESULTS: The mean (+/-SD) HAQ-DI score at entry was 1.04 +/- 0.67. Fifty-three percent of patients had HAQ-DI scores > or = 1.0 (signifying moderate-to-severe functional impairment). Multivariate logistic regression demonstrated that impaired fist closure > or = 23 mm (OR 4.24, 95% CI 1.68-10.70), reduced handspread < or = 175 mm (OR 4.5, 95% CI 1.80-11.24), joint tenderness count > or = 1.0 (OR 2.93, 95% CI 1.16-7.40), age > or = 43 years (OR 2.44, 95% CI 1.01-5.95), platelet count > or = 330,000/mm3 (OR 2.30, 95% CI 0.96-5.57), and female sex (OR 2.43, 95% CI 0.77-7.73) were the most important correlates of HAQ-DI scores > or = 1.0. CONCLUSION: Increased HAQ-DI scores at baseline were correlated with reduced fist closure, reduced hand-spread, elevated platelet count, presence of tender joints, older age, and female sex. The most important contributor to functional impairment was hand dysfunction. Even within the first 18 months after SSc onset, moderate-severe functional impairment (HAQ-DI scores > or = 1.0) was frequent (53%) in this group of diffuse SSc patients. In early diffuse SSc, the self-administered HAQ-DI is therefore a valuable assessment of function that correlates with objective physical and laboratory measures of SSc disease involvement. Abnormal HAQ-DI scores may support patient claims of functional impairment, help to focus physician attention on implementing measures to reduce functional impairment, and be useful in reflecting the disease course over time.

Adolescent↗

PubMed1999

A randomized controlled trial of individual psychological debriefing for victims of violent crime.

BACKGROUND: It has been suggested that giving people the opportunity talk about a traumatic experience may prevent the development of later disorder. We tested the efficacy of two brief interventions, education and psychological debriefing, designed to prevent adverse psychological reactions to criminal victimization. METHODS: Individuals who had been the victims of a violent crime within the past month were written to and invited to take part in a study of their attitudes to crime and punishment: 2161 were contacted and 243 replied, of whom 157 were eligible and were randomly assigned either to an education condition, to a psychological debriefing plus education condition, or to an assessment only condition. Education involved providing information about normal post-traumatic reactions. Debriefing involved in-depth probing about events, thoughts and feelings experienced during the crime. Subjects were recruited from police and hospital sources and interviewed in their own homes: 138 were followed up at 6 months, and 92 at 11 months. RESULTS: Outcome was assessed using a DSM-III-R diagnosis of PTSD, the Post-traumatic Symptom Scale, the Impact of Event Scale and the Beck Depression Inventory. All groups improved over time but there were no between-group differences. CONCLUSIONS: No evidence was found to support the efficacy of brief one-session interventions for preventing post-traumatic symptoms in individual victims of violent crime.

Adolescent↗

PubMed1999

Paraplegia: prolonged standing using closed-loop functional electrical stimulation and Andrews ankle-foot orthosis.

One T10 paraplegic male (CS) implanted in 1991 with a Nucleus FES-22 stimulator has been able to achieve closed-loop standing for 1 h. The knee angles are monitored by electrogoniometers, resulting in the quadriceps stimulation time being less than 10%. Stance stability is achieved by the Andrews anterior ankle-foot orthosis (AFO). The use of accelerometers for trunk inclination and vertical acceleration during controlled stand-to-sit, diminishes slamming onto the seat. CS does one-handed tasks with objects of 2.2 kg. In another T10 paraplegic male (FR), surface stimulation was applied over 1.5 years to both femoral nerves at the groin for conditioning and prolonged standing. With quadricep conditioning, 55 Nm at 45 degrees of knee flexion is produced. With the AFO and knee monitoring, FR can stand uninterrupted for up to 70 min and perform one-handed tasks. In August 1998, he was implanted with the multifunctional Praxis FES 24-A stimulator for restoration of limb movements, bladder and bowel function, and pressure sore prevention.

Acceleration↗

PubMed1999

In vivo analysis of the domains of yeast Rvs167p suggests Rvs167p function is mediated through multiple protein interactions.

Morphological changes during cell division in the yeast Saccharomyces cerevisiae are controlled by cell-cycle regulators. The Pcl-Pho85p kinase complex has been implicated in the regulation of the actin cytoskeleton at least in part through Rvs167p. Rvs167p consists of three domains called BAR, GPA, and SH3. Using a two-hybrid assay, we demonstrated that each region of Rvs167p participates in protein-protein interactions: the BAR domain bound the BAR domain of another Rvs167p protein and that of Rvs161p, the GPA region bound Pcl2p, and the SH3 domain bound Abp1p. We identified Rvs167p as a Las17p/Bee1p-interacting protein in a two-hybrid screen and showed that Las17p/Bee1p bound the SH3 domain of Rvs167p. We tested the extent to which the Rvs167p protein domains rescued phenotypes associated with deletion of RVS167: salt sensitivity, random budding, and endocytosis and sporulation defects. The BAR domain was sufficient for full or partial rescue of all rvs167 mutant phenotypes tested but not required for the sporulation defect for which the SH3 domain was also sufficient. Overexpression of Rvs167p inhibits cell growth. The BAR domain was essential for this inhibition and the SH3 domain had only a minor effect. Rvs167p may link the cell cycle regulator Pcl-Pho85p kinase and the actin cytoskeleton. We propose that Rvs167p is activated by phosphorylation in its GPA region by the Pcl-Pho85p kinase. Upon activation, Rvs167p enters a multiprotein complex, making critical contacts in its BAR domain and redundant or minor contacts with its SH3 domain.

Cytoskeletal Proteins↗

PubMed1999

Regulation of cell cycle transcription factor Swi4 through auto-inhibition of DNA binding.

In Saccharomyces cerevisiae, two transcription factors, SBF (SCB binding factor) and MBF (MCB binding factor), promote the induction of gene expression at the G(1)/S-phase transition of the mitotic cell cycle. Swi4 and Mbp1 are the DNA binding components of SBF and MBF, respectively. The Swi6 protein is a common subunit of both transcription factors and is presumed to play a regulatory role. SBF binding to its target sequences, the SCBs, is a highly regulated event and requires the association of Swi4 with Swi6 through their C-terminal domains. Swi4 binding to SCBs is restricted to the late M and G(1) phases, when Swi6 is localized to the nucleus. We show that in contrast to Swi6, Swi4 remains nuclear throughout the cell cycle. This finding suggests that the DNA binding domain of Swi4 is inaccessible in the full-length protein when not complexed with Swi6. To explore this hypothesis, we expressed Swi4 and Swi6 in insect cells by using the baculovirus system. We determined that partially purified Swi4 cannot bind SCBs in the absence of Swi6. However, Swi4 derivatives carrying point mutations or alterations in the extreme C terminus were able to bind DNA or activate transcription in the absence of Swi6, and the C terminus of Swi4 inhibited Swi4 derivatives from binding DNA in trans. Full-length Swi4 was determined to be monomeric in solution, suggesting an intramolecular mechanism for auto-inhibition of binding to DNA by Swi4. We detected a direct in vitro interaction between a C-terminal fragment of Swi4 and the N-terminal 197 amino acids of Swi4, which contain the DNA binding domain. Together, our data suggest that intramolecular interactions involving the C-terminal region of Swi4 physically prevent the DNA binding domain from binding SCBs. The interaction of the carboxy-terminal region of Swi4 with Swi6 alleviates this inhibition, allowing Swi4 to bind DNA.

Amino Acid Sequence↗

PubMed1999

Acute stress disorder and posttraumatic stress disorder in victims of violent crime.

OBJECTIVE: In a group of crime victims recruited from the community, the authors investigated the ability of both a diagnosis of acute stress disorder and its component symptoms to predict posttraumatic stress disorder (PTSD) at 6 months. METHOD: A mixed-sex group of 157 victims of violent assaults were interviewed within 1 month of the crime. At 6-month follow-up 88% were reinterviewed by telephone and completed further assessments generating estimates of the prevalence of PTSD. RESULTS: The rate of acute stress disorder was 19%, and the rate of subsequent PTSD was 20%. Symptom clusters based on the DSM-IV criteria for acute stress disorder were moderately strongly interrelated. All symptom clusters predicted subsequent PTSD, but not as well as an overall diagnosis of acute stress disorder, which correctly classified 83% of the group. Similar predictive power could be achieved by classifying the group according to the presence or absence of at least three reexperiencing or arousal symptoms. Logistic regression indicated that both a diagnosis of acute stress disorder and high levels of reexperiencing or arousal symptoms made independent contributions to predicting PTSD. CONCLUSIONS: This exploratory study provides evidence for the internal coherence of the new acute stress disorder diagnosis and for the symptom thresholds proposed in DSM-IV. As predicted, acute stress disorder was a strong predictor of later PTSD, but similar predictive power may be possible by using simpler criteria.

Acute Disease↗

PubMed1999

Characteristics, context and consequences of memory recovery among adults in therapy.

BACKGROUND: There are concerns that memories recovered during therapy are likely to be the result of inappropriate therapeutic techniques. AIMS: To investigate systematically these concerns. METHOD: One-hundred and eight therapists provided information on all clients with recovered memories seen in the past three years, and were interviewed in detail on up to three such clients. RESULTS: Of a total of 690 clients, therapists reported that 65% recalled child sexual abuse and 35% recalled other traumas, 32% started recovering memories before entering therapy. According to therapists' accounts, among the 236 detailed client cases very few appeared improbable and corroboration was reported in 41%. Techniques to aid recall were used in 42%, but only in 22% were they used before memory recovery started. CONCLUSIONS: Some of the data are consistent with memories being of iatrogenic origin, but other data clearly point to the need for additional explanations.

Age Distribution↗

PubMed1998

Interaction of yeast Rvs167 and Pho85 cyclin-dependent kinase complexes may link the cell cycle to the actin cytoskeleton.

BACKGROUND: . PHO85 encodes the catalytic subunit of a cyclin-dependent kinase (Cdk) in budding yeast and functions in phosphate and glycogen metabolism. Pho85 associated with the G1 cyclins Pcl1 and Pcl2 is also required for cell cycle progression in the absence of the Cdc28 cyclins Cln1 and Cln2. Loss of Pcl1, Pcl2 and related Pho85 cyclins results in budding defects, suggesting that Pcl-Pho85 complexes function in cell morphogenesis early in the cell cycle; their precise role is not clear, however. RESULTS: . To identify targets for Pcl-Pho85 kinases, we performed yeast two-hybrid interaction screens using Pcl2 and the related cyclin Pcl9. We identified RVS167, a gene involved in endocytosis, organization of the actin cytoskeleton, and cell survival after starvation. Like rvs167Delta mutants, pho85 mutants or strains deleted for the Pcl1,2-type Pho85 cyclins showed abnormal cell morphology on starvation, sensitivity to salt, random budding in diploids, and defects in endocytosis and in the actin cytoskeleton. Overexpression of Rvs167 in wild-type cells caused morphological abnormalities and growth arrest at high temperatures; these phenotypes were exacerbated by deleting PHO85. Rvs167 has a Src homology 3 (SH3) domain and five potential Pho85 phosphorylation sites; recombinant Rvs167 was phosphorylated by the Pcl2-Pho85 kinase in vitro. Maximal phosphorylation of Rvs167 in vivo required Pho85 and the Pcl1,2-type cyclins. CONCLUSIONS: . Rvs167 interacts with Pho85 cyclins and is implicated as a target of Pho85 kinases in vivo. Our results identify a connection between Cdks and the actin cytoskeleton; interaction of Rvs167 and Pcl-Pho85 Cdks might contribute to actin cytoskeleton regulation in response to stresses such as starvation.

Actins↗

PubMed1998

The cyclin family of budding yeast: abundant use of a good idea.

Cyclins are highly conserved proteins that activate cyclin-dependent kinases (CDKs) to regulate the cell cycle, transcription and other cellular processes. The completion of the genome sequence of the budding yeast Saccharomyces cerevisiae allows an appraisal of the functions of the entire complement of cyclins in a eukaryotic organism. The cyclin family of budding yeast is reviewed from a functional perspective with an emphasis on what genetic and biochemical experiments have revealed about cyclin-CDK substrates.

Animals↗

PubMed1998

Recovered memories of trauma: phenomenology and cognitive mechanisms.

We outline four current explanations for the reported forgetting of traumatic events, namely repression, dissociation, ordinary forgetting, and false memory. We then review the clinical and survey evidence on recovered memories, and consider experimental evidence that a variety of inhibitory processes are involved in everyday cognitive activity including forgetting. The data currently available do not allow any of the four explanations to be rejected, and strongly support the likelihood that some recovered memories correspond to actual experiences. We propose replacing the terms repression and dissociation as explanations of forgetting with an account based on cognitive science.

Amnesia↗

PubMed1998

Cyclin partners determine Pho85 protein kinase substrate specificity in vitro and in vivo: control of glycogen biosynthesis by Pcl8 and Pcl10.

In Saccharomyces cerevisiae, PHO85 encodes a cyclin-dependent protein kinase (Cdk) with multiple roles in cell cycle and metabolic controls. In association with the cyclin Pho80, Pho85 controls acid phosphatase gene expression through phosphorylation of the transcription factor Pho4. Pho85 has also been implicated as a kinase that phosphorylates and negatively regulates glycogen synthase (Gsy2), and deletion of PHO85 causes glycogen overaccumulation. We report that the Pcl8/Pcl10 subgroup of cyclins directs Pho85 to phosphorylate glycogen synthase both in vivo and in vitro. Disruption of PCL8 and PCL10 caused hyperaccumulation of glycogen, activation of glycogen synthase, and a reduction in glycogen synthase kinase activity in vivo. However, unlike pho85 mutants, pcl8 pcl10 cells had normal morphologies, grew on glycerol, and showed proper regulation of acid phosphatase gene expression. In vitro, Pho80-Pho85 complexes effectively phosphorylated Pho4 but had much lower activity toward Gsy2. In contrast, Pcl10-Pho85 complexes phosphorylated Gsy2 at Ser-654 and Thr-667, two physiologically relevant sites, but only poorly phosphorylated Pho4. Thus, both the in vitro and in vivo substrate specificity of Pho85 is determined by the cyclin partner. Mutation of PHO85 suppressed the glycogen storage deficiency of snf1 or glc7-1 mutants in which glycogen synthase is locked in an inactive state. Deletion of PCL8 and PCL10 corrected the deficit in glycogen synthase activity in both the snf1 and glc7-1 mutants, but glycogen synthesis was restored only in the glc7-1 mutant strain. This genetic result suggests an additional role for Pho85 in the negative regulation of glycogen accumulation that is independent of Pcl8 and Pcl10.

Cyclin-Dependent Kinases↗