Yeast Artificial Chromosomes

Yeast artificial chromosomes (YACs) are shuttle-vectors that can be amplified in bacteria and employed for the cloning and manipulation of large deoxyribonucleic acid (DNA) inserts (up to 3 Mb pairs) in the yeast Saccharomyces cerevisiae. Artificial chromosomes can be conveniently built and modified in yeast cells using in vivo homologous recombination, a novel process known as ‘recombineering’. The capacity of YACs to accommodate large DNA fragments is exploited to clone clusters of genes surrounded by their native DNA context, where regulatory elements are located. This is important for biotechnology, when YACs are used for engineering genetic determinants of new biochemical pathways for production of secondary metabolites and for heterologous protein expression. YACs can be retrofitted with the appropriate selectable markers and transmitted to cells of different organisms allowing the generation of transgenic animals. Finally, YACs are largely employed in the production of full-scale genomic libraries, for mapping and functional analysis purposes. Key Concepts: Yeast artificial chromosomes (YACs) represent the top instruments for the study of eukaryotic genomes and for mobilisation of large genetic elements among bacteria and eukaryotes. YACs behave like naturally existing chromosomes, provided that they are of the proper size, showing comparable stability. YACs can be manipulated directly by classical genetic engineering as well as by modern recombineering technology. Properly retrofitted, YACs can be used in many different organisms, for cloning or genome analysis. Chromosomal translocation can be studied using disposable YACs that do not harbour genetic information essential for cell function. Keywords: ARS; centromere; DNA cloning; genome manipulation; genomic library; recombineering; recombinagenic targeting; telomere; transgenic organism; yeast vector