FND-Cell cycle

The Yeast Cell Cycle

 

Keywords:  Yeast cell cycle review;

 

 

Caution!

This unit is under development. There is some contents here but it is incomplete and/or may change significantly: links may lead to nowhere, the contents is likely going to be rearranged, and objectives, deliverables etc. may be incomplete or missing. Do not work with this material until it is updated to "live" status.

 

Abstract

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This unit ...

Prerequisites

You need the following preparation before beginning this unit. If you are not familiar with this material from courses you took previously, you need to prepare yourself from other information sources:

• Cell cycle: Replication control and mechanism; phases of the cell-cycle; checkpoints and apoptosis.

 

Objectives

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Outcomes

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Deliverables

• Time management: Before you begin, estimate how long it will take you to complete this unit. Then, record in your course journal: the number of hours you estimated, the number of hours you worked on the unit, and the amount of time that passed between start and completion of this unit.
• Journal: Document your progress in your course journal.
• Insights: If you find something particularly noteworthy about this unit, make a note in your insights! page.

 

Evaluation

Evaluation: NA

This unit is not evaluated for course marks.

 

Contents

Task:

• Read the introductory notes on cell cycle concepts.

 

Principles

McInerny (2016) Cell cycle regulated transcription: from yeast to cancer. F1000Res 5:. (pmid: 27239285)

[ PubMed ] [ DOI ] Recent studies have revealed exciting new functions for forkhead transcription factors in cell proliferation and development. Cell proliferation is a fundamental process controlled by multiple overlapping mechanisms, and the control of gene expression plays a major role in the orderly and timely division of cells. This occurs through transcription factors regulating the expression of groups of genes at particular phases of the cell division cycle. In this way, the encoded gene products are present when they are required. This review outlines recent advances in our understanding of this process in yeast model systems and describes how this knowledge has informed analysis in more developmentally complex eukaryotes, particularly where it is relevant to human disease.

McInerny (2011) Cell cycle regulated gene expression in yeasts. Adv Genet 73:51-85. (pmid: 21310294)

[ PubMed ] [ DOI ] The regulation of gene expression through the mitotic cell cycle, so that genes are transcribed at particular cell cycle times, is widespread among eukaryotes. In some cases, it appears to be important for control mechanisms, as deregulated expression results in uncontrolled cell divisions, which can cause cell death, disease, and malignancy. In this review, I describe the current understanding of such regulated gene expression in two established simple eukaryotic model organisms, the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe. In these two yeasts, the global pattern of cell cycle gene expression has been well described, and most of the transcription factors that control the various waves of gene expression, and how they are in turn themselves regulated, have been characterized. As related mechanisms occur in all other eukaryotes, including humans, yeasts offer an excellent paradigm to understand this important molecular process.

The yeast Mbp1 protein

Taylor et al. (2000) Characterization of the DNA-binding domains from the yeast cell-cycle transcription factors Mbp1 and Swi4. Biochemistry 39:3943-54. (pmid: 10747782)

[ PubMed ] [ DOI ] The minimal DNA-binding domains of the Saccharomyces cerevisiae transcription factors Mbp1 and Swi4 have been identified and their DNA binding properties have been investigated by a combination of methods. An approximately 100 residue region of sequence homology at the N-termini of Mbp1 and Swi4 is necessary but not sufficient for full DNA binding activity. Unexpectedly, nonconserved residues C-terminal to the core domain are essential for DNA binding. Proteolysis of Mbp1 and Swi4 DNA-protein complexes has revealed the extent of these sequences, and C-terminally extended molecules with substantially enhanced DNA binding activity compared to the core domains alone have been produced. The extended Mbp1 and Swi4 proteins bind to their cognate sites with similar affinity [K(A) approximately (1-4) x 10(6) M(-)(1)] and with a 1:1 stoichiometry. However, alanine substitution of two lysine residues (116 and 122) within the C-terminal extension (tail) of Mbp1 considerably reduces the apparent affinity for an MCB (MluI cell-cycle box) containing oligonucleotide. Both Mbp1 and Swi4 are specific for their cognate sites with respect to nonspecific DNA but exhibit similar affinities for the SCB (Swi4/Swi6 cell-cycle box) and MCB consensus elements. Circular dichroism and (1)H NMR spectroscopy reveal that complex formation results in substantial perturbations of base stacking interactions upon DNA binding. These are localized to a central 5'-d(C-A/G-CG)-3' region common to both MCB and SCB sequences consistent with the observed pattern of specificity. Changes in the backbone amide proton and nitrogen chemical shifts upon DNA binding have enabled us to experimentally define a DNA-binding surface on the core N-terminal domain of Mbp1 that is associated with a putative winged helix-turn-helix motif. Furthermore, significant chemical shift differences occur within the C-terminal tail of Mbp1, supporting the notion of two structurally distinct DNA-binding regions within these proteins.

Deleeuw et al. (2008) Thermodynamics and specificity of the Mbp1-DNA interaction. Biochemistry 47:6378-85. (pmid: 18491920)

[ PubMed ] [ DOI ] The DNA binding domain of the yeast transcription factor Mbp1 is a winged helix-turn-helix structure, with an extended DNA binding site involving C-terminal "tail" residues. The thermodynamics of the interaction of the DNA binding domain with its target DNA sequence have been determined using fluorescence anisotropy and calorimetry. The dissociation constant was determined as a function of pH and ionic strength in assessing the relative importance of specific and nonspecific ionic interactions. Mutational analysis of the residues in the binding site was used to determine their contributions to binding. The three tail histidine residues and His 63 in the recognition helix accounted for most of the pH dependence of the DNA binding. The tail histidine residues, along with two previously identified lysine residues, account for a major part of the polyelectrolyte contribution to binding and for the nonspecific affinity of Mbp1 for DNA. Gln67 was shown to be a very important residue, which interacts in the minor groove of the target DNA. Systematic mutations of the DNA consensus binding sites showed that the CGCG core contributes most to recognition. Isothermal titration calorimetry revealed a strong temperature-dependent enthalpy change, with a Delta Cp of -1.3kJ mol(-1) K(-1), consistent with a specific binding mode and burial of surface area. Parsing the free energy contributions demonstrates that polyelectrolyte effects account for half of the total free energy at the physiological pH and salt concentration. We present a model for the origin of the sequence specificity and overall affinity of the protein that accounts for the observed thermodynamics.

Chernatynskaya et al. (2009) Structural analysis of the DNA target site and its interaction with Mbp1. Org Biomol Chem 7:4981-91. (pmid: 19907790)

[ PubMed ] [ DOI ] The solution structure of a 14 base-pair non-self complementary DNA duplex containing the consensus-binding site of the yeast transcription factor Mbp1 has been determined by NMR using a combination of scalar coupling analysis, time-dependent NOEs, residual dipolar couplings and 13C-edited NMR spectroscopy of a duplex prepared with one strand uniformly labeled with 13C-nucleotides. As expected, the free DNA duplex is within the B-family of structures, and within experimental limits is straight. However, there are clear local structural variations associated with the consensus CGCG element in the binding sequence that are important for sequence recognition. In the complex, the DNA bends around the protein, which also undergoes some conformational rearrangement in the C-terminal region. Structural constraints derived from paramagnetic perturbation experiments with spin-labeled DNA, chemical shift perturbation experiments of the DNA, previous cross-saturation, chemical shift perturbation experiments on the protein, information from mutational analysis, and electrostatics calculations have been used to produce a detailed docked structure using the known solution conformation of the free protein and other spectroscopic information about the Mbp1:DNA complex. A Monte Carlo-based docking procedure with restrained MD in a fully solvated system subjected to available experimental constraints produced models that account for the available structural data, and can rationalize the extensive thermodynamic data about the Mbp1:DNA complex. The protein:DNA interface is closely packed and is associated with a small number of specific contacts. The structure shows an extensive positively charged surface that accounts for the high polyelectrolyte contribution to binding.

 

Further reading, links and resources

 

Notes

 

Self-evaluation

 

 

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About ...
 
Author:

Boris Steipe <boris.steipe@utoronto.ca>

Created:

2017-08-05

Modified:

2017-08-05

Version:

0.1

Version history:

• 0.1 First stub

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