Ripon College1, Chemistry, Ripon, WI 54971 Harvard Medical School2, Cell Biology, Boston, MA 02115
The protein Swi6 is an important structural component of heterochromatic, or silent, regions of chromosomes in the fission yeast Schizosaccharomyces pombe. This protein is essential for the assembly and maintenance of heterochromatin, as the lack of Swi6 leads to a loss of both silencing and proper chromosome segregation during mitosis. Swi6 contains a chromodomain and can bind directly to chromatin, but also co-immunoprecipitates with several other proteins. In addition, Swi6 is hypothesized to form oligomers, aiding in the spreading of heterochromatin along the chromosome. These observations suggest that Swi6 may have multiple functions in the formation and maintenance of heterochromatin. To provide a starting point for determining these additional functions of Swi6, we used PCR-based mutagenesis coupled with in vivo gap repair to screen for dominant-negative alleles of the swi6+ gene that compromise its silencing activity. Dominant-negative phenotypes were identified by the de-repression of the ade6 reporter gene inserted inside the heterochromatic locus found near the yeast centromere. The characterization of these mutations will reveal important regions of Swi6 that can be targeted in future studies of its structure and function.
[Abstract (DOC)]