TY - JOUR
T1 - Clb5-associated kinase activity is required early in the spindle pathway for correct preanaphase nuclear positioning in Saccharomyces cerevisiae
AU - Segal, Marisa
AU - Clarke, Duncan J.
AU - Reed, Steven I.
PY - 1998/10/5
Y1 - 1998/10/5
N2 - In Saccharomyces cerevisiae, a single cyclin-dependent kinase, Cdc28, regulates both G1/S and G2/M phase transitions by associating with stage- specific cyclins. During progression through S phase and G2/M, Cdc28 is activated by the B-type cyclins Clb1-6. Because of functional redundancy, specific roles for individual Clbs have been difficult to assign. To help genetically define such roles, strains carrying a cdc28(ts) allele, combined with single CLB deletions were studied. We assumed that by limiting the activity of the kinase, these strains would be rendered more sensitive to loss of individual Clbs. By this approach, a novel phenotype associated with CLB5 mutation was observed. Homozygous cdc28-4(ts) clb5 diploids were inviable at room temperature. Cells were defective in spindle positioning, leading to migration of undivided nuclei into the bud. Occasionally, misplaced spindles were observed in cdc28-4 clb5 haploids; additional deletion of CLB6 caused full penetrance. Thus, CLB5 effects proper preanaphase spindle positioning, yet the requirement differs in haploids and diploids. The execution point for the defect corresponded to the time of Clb5-dependent kinase activation. Nevertheless, lethality of cdc28-4 clb5 diploids was not rescued by CLB2 or CLB4 overexpression, indicating a specificity of Clb5 function beyond temporality of expression.
AB - In Saccharomyces cerevisiae, a single cyclin-dependent kinase, Cdc28, regulates both G1/S and G2/M phase transitions by associating with stage- specific cyclins. During progression through S phase and G2/M, Cdc28 is activated by the B-type cyclins Clb1-6. Because of functional redundancy, specific roles for individual Clbs have been difficult to assign. To help genetically define such roles, strains carrying a cdc28(ts) allele, combined with single CLB deletions were studied. We assumed that by limiting the activity of the kinase, these strains would be rendered more sensitive to loss of individual Clbs. By this approach, a novel phenotype associated with CLB5 mutation was observed. Homozygous cdc28-4(ts) clb5 diploids were inviable at room temperature. Cells were defective in spindle positioning, leading to migration of undivided nuclei into the bud. Occasionally, misplaced spindles were observed in cdc28-4 clb5 haploids; additional deletion of CLB6 caused full penetrance. Thus, CLB5 effects proper preanaphase spindle positioning, yet the requirement differs in haploids and diploids. The execution point for the defect corresponded to the time of Clb5-dependent kinase activation. Nevertheless, lethality of cdc28-4 clb5 diploids was not rescued by CLB2 or CLB4 overexpression, indicating a specificity of Clb5 function beyond temporality of expression.
KW - Cell cycle
KW - Nuclear migration
KW - Spindle dynamics
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U2 - 10.1083/jcb.143.1.135
DO - 10.1083/jcb.143.1.135
M3 - Article
C2 - 9763426
AN - SCOPUS:0032487521
SN - 0021-9525
VL - 143
SP - 135
EP - 145
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 1
ER -