Molecular Cell Biology of the Yeast Saccharomyces cerevisiae

Molecular Cell Biology of the Yeast Saccharomyces cerevisiae Lecture III: Molecular Logic of Asymmetry Zhang Yi, National Institute of Biological Sciences, 20080628

Cellular Anatomy

Mitosis V. S Meiosis α α a a

Mating Type Switch

Mating Type Specific Gene • MATa gene expression – a 1 m. RNA from MATa locus – Other a-specific gene expression is default • Driven by MCM 1 homodimer • MAT gene expression – 1, 2 m. RNA from MAT – 1 and 2 function • Repress a-specific genes – 2/MCM 1 heterodimer • Stimulate -specific genes – 1/MCM 1 heterodimer

Mating Type Specific Gene Expression

Mating Type Switch Mechanism: HO

Mating Type Switch Mechanism: hetero-sequence switch

Recombination Enhancer Sequence

Sequence-Specific RE Effects

RE Sequence Shows Mat. Alpha 2 Binding Site

RE Mutants Render Chromatin Structural Change wt … mt …

A Mcm 1 p Binding Site in RE is Necessary for RE Function

Mat. Alpha 2 Interaction with Tup 1/Ssn 6 is Essential for Haploid/a-specific Gene Repression

Tup 1/Ssn 6 Complex is Global Transcription Suppressor Associated with HDACs

A Model Summarizing Mcm 1 p-Mediated Chromosomal Effects on RE and Other Loci

Evolution of the Molecular Logic of Mating Type in Fungi S. Pombe

Maternal Effect on Mating Type Switch ? ? ?

HO Promoter Dissection

HO Expression Depends on Swi/Snf Complex: LOF and GOF

Ash 1 p Represses Mating Type Switch in Daughter Cell by Inhibiting HO Expression

Ash 1 p and Swi/Snf Show Reciprocal Effects on Mating Type Switch

Ash 1 p Localization Dependence: Genetic Screen for mother cells who do NOT express HO (promoter is inhibited) as a consequence of any genetic defect

She Genes are Necessary for HO Expression

She 1 p/5 p are Cytoskeletal Proteins, and Some She Genes are Localized to Daughter Cells Interdependence of She genes on localization

Actin-dependent Ash 1 m. RNA Localization into Daughter Cell FISH Genetics LOF Pharmacology LOF Genetics GOF

She genes and Ash 1 m. RNP transport

Visualizing m. RNA Transport

Local Translation

Local Translation Regulation is as Essential as Localization

Protein Level in Temporal Context Degredation for old alpha 2 as well as HO etc

Protein Dynamics not Limited to Ash 1 m. RNA Transportation