You isolate a temperature sensitive mutant cell linethat fails to divide at the non-permissive temperature and notice that Cdk24p expression is not downregulated after S phase at the non permissive temperature - it remains constitutively high. Using standard techniques, you isolate the gene that is mutated in the temperature-sensitive cell line; it is a previously undescribed gene, Cdc927, encoding a protein with two "zinc fingers" that, upon comparison to the database, fall into the category of a "ring" domain--similar to those seen in E3 ubiquitin ligases. The mutant that you isolated has a cdc927 mutation altering an arginine near a conserved cysteine within the ring domain.
Interestingly, you find that in cells with this cdc927 mutation, a panel of 8 cell cycle associated proteins fail to be down-regulated after S phase at the nonpermissive temperature. mRNA levels for all of these proteins are constant throughout the cell cycle in wild-type cells. Moreover, temperature-sensitive mutants of proteasome subunits also produce the same phenotype as the cdc927 mutant, i.e. stabilization of all 8 proteins.
Ans- a. Cdc927p likely act on Mitosis (M) phase of cell cycle because it is similar as E3 ubiquitin ligase and this ligase act on M-phase of cycle for targeting the substrate for destruction by proteosome. This ligase also contain Anaphase promoting complex (APC) and Skp1-Cullin-F-box protein complex (SCF complex). APC/C main function is helps in transition from metaphase to Anaphase by specific protein degradation.
Inspired by Lee Hartwell's Nobel Prize (2001), you decide to study cell cycle regulation in yeast....
1. You are characterizing a temperature-sensitive mutant called nlk1 in Saccharomyces cerevisiae. To examine whether the mutant has a defect in cell cycle progression, you perform two experiments. First, you try flow cytometry with samples of the mutant strain incubated at the permissive or non-permissive temperatures A wildtype strain incubated at each temperature is a used as control. The flow cytometry results are shown below in Panel A. Second, you examine the Nlk1 protein levels throughout the cell cycle in...
Eukaryote gene regulation question... about the yeast... please help me... 3. (7 points total) You are studying a set of genes in yeast (a eukaryote) that are required for the utilization of mannose. Mannose is a sugar that can be used by yeast cells but they will preferentially use glucose if it is available; this is similar to how the galactose genes work. Since you are a geneticist you study the genes by mutating them so they won't work and...
2. A dominant allele H reduces the number of body bristles that Drosophila flies have, giving rise to a “hairless” phenotype. In the homozygous condition, H is lethal. An independently assorting dominant allele S has no effect on bristle number except in the presence of H, in which case a single dose of S suppresses the hairless phenotype, thus restoring the "hairy" phenotype. However, S also is lethal in the homozygous (S/S) condition. What ratio of hairy to hairless flies...