Methods designed for the identification and characterization ofin vitro andin vivo chromatin assembly mutants inSaccharomyces cerevisiae

Assembly of
DNA
into chromatin allows for the formation of a barrier that protects naked DNA from protein and chemical agents geared to degrade or metabolize DNA. Chromatin assembly occurs whenever a length of DNA becomes exposed to the cellular elements, whether during DNA synthesis or repair. This report describes tools to study chromatin assembly in the model system
Saccharomyces cerevisiae
. Modifications to an
in vitro
chromatin assembly assay are described that allowed a brute force screen of temperature sensitive (
ts
) yeast strains in order to identify chromatin assembly defective extracts. This screen yielded mutations in genes encoding two ubiquitin protein ligases (E3s):
RSP5
, and a subunit of the Anaphase Promoting Complex (APC),
APC5
. Additional modifications are described that allow for a rapid analysis and an
in vivo
characterization of yeast chromatin assembly mutants, as well as any other mutant of interest. Our analysis suggests that the
in vitro
and
in vivo
chromatin assembly assays are responsive to different cellular signals, including cell cycle cues that involve different molecular networks.