Chapter 11 Yeast Minichromosomes

This chapter discusses the advantages and disadvantages of minichromosomes as an experimental system and reviews some of the questions regarding chromatin structure, which are successfully addressed using yeast minichromosomes. It describes general methods for their isolation, with an analysis of the strengths and weaknesses of each in regard to particular applications. Saccharomyces cerevisiae chromatin comprises nucleosomal subunits containing the four core histone molecules that are highly conserved among all eukaryotes. The chapter also describes mapping techniques useful in determining nucleosome position. The episomal DNA is packaged into chromatin in yeast. Although yeast plasmids may lack centromeres and do lack telomeres, they are often referred to as “minichromosomes,” using nomenclature introduced for viral episomes in higher eukaryotes. Yeast minichromosomes have provided a unique model system for study of many aspects of chromatin structure. Yeast minichromosomes provide an in vivo system. The ability to manipulate the genetic background of the host yeast cell together with the relative ease with which plasmid chromatin can be isolated and analyzed make yeast minichromosomes a very powerful system to study the structure of chromatin and also the functional consequences of changes in chromatin structure.