A new yeast artificial chromosome vector designed for gene transfer into mammalian cells

A yeast artificial chromosome-splitting vector designed for precise manipulation of specific plant chromosome region

A yeast artificial chromosome (YAC) splitting vector, pKI01, was constructed for manipulating plant chromosome fragments cloned as YACs in order to transfer specific regions of the fragments into plant cells. Vector pKI01 consists of Km(r) and ADE2 genes (selective markers for plant and yeast transformants, respectively), inverted telomeric repeats Tr and CEN4. To demonstrate the utility of pKI01, YAC CIC9e2 harboring a 590-kb fragment from Arabidopsis thaliana chromosome 5 was split into specific fragments. A 1-kb target region positioned 100 kb from the right end of the 590 kb fragment was cloned into pKI01. The resultant plasmid, pKY03, was introduced into Saccharomyces cerevisiae harboring YAC CIC9e2. The Ade+ transformants were found to contain two new YACs of 490 and 100 kb, and to lack the original 590 kb YAC, consistent with the expected splitting event. To release the desired middle region of YAC CIC9e2, two additional splitting vectors were constructed, pKY11 and pKY14. By conducting two rounds of splitting, i.e., the first round 100 kb from the right end of YAC CIC9e2 with pKY11 to generate 490 and 100 kb YACs and a second round 50 kb from the right end of the new 490 kb YAC to generate 440 and 50 kb YACs, the middle 50 kb region of a plant chromosome fragment harboring Km(r) was successfully released as a split YAC. These results indicate that YAC splitting vectors as constructed in this study are useful for generating any desired plant chromosome fragment as a YAC for eventual re-introduction into plant cells.

Exploiting the yeast Saccharomyces cerevisiae for the study of the organization and evolution of complex genomes

Yeast artificial chromosome (YAC) cloning systems have advanced the analysis of complex genomes considerably. They permit the cloning of larger fragments than do bacterial artificial chromosome systems, and the cloned material is more easily modified. We recently developed a novel YAC cloning system called transformation-associated recombination (TAR) cloning. Using in vivo recombination in yeast, TAR cloning selectively isolates, as circular YACs, desired chromosome segments or entire genes from complex genomes. The ability to do that without constructing a representative genomic library of random clones greatly facilitates analysis of gene function and its role in disease. In this review, we summarize how recombinational cloning techniques have advanced the study of complex genome organization, gene expression, and comparative genomics.