Dissection of centromeric DNA from yeast Yarrowia lipolytica and identification of protein-binding site required for plasmid transmission.

In a dimorphic yeast, Yarrowia lipolytica, replicative plasmids can be established only in the coexistence of the replication origin (ORI) and centromere (CEN) from its own chromosomal DNA. Although six CEN sequences so far isolated from this yeast exhibit no similarity with conventional CEN DNA elements from other budding yeasts, they are confined within short regions (approximately 0.2 kb) and contain various conserved sequence blocks. We surveyed here a CEN1-1 sequence on an ORI-containing plasmid by deletion and site-directed mutagenesis, and found a partial palindrome, CCTAATTTGG designated DS9, to be an essential element for high-efficiency transformation. In particular, point mutations that alter symmetry and/or length of the palindrome abrogated the activity of CEN1-1. Gel mobility shift assay of CEN1-1 DNA fragments incubated with Y. lipolytica nuclear proteins revealed four bands corresponding to protein-DNA complexes, whereas the mutations within DS9 that disabled transformation also abolished the formation of part of these complexes, depending on particular mutations. These results demonstrate that the palindrome is a binding site for specific protein(s) necessary for plasmid transmission in Y. lipolytica.