Molecular Genetics

Replication origins can be identified by their ability to bind an ORC and by other methods.

Facts

	A quantitative measure of ARS activity can be obtained by calculating the proportion of progeny cells that contain the transforming DNA, the plasmid stability. Mutation of the ARS consensus sequence destroys the plasmid stability. Separate mutations within two or three other regions of ARS reduce, but do not eliminate, plasmid stability. Combined, the mutations almost abolish plasmid stability.
Studies with ARS sequences and origins from eukaryotic viruses suggest that origins can be though of as containing an origin recognition element, a DNA unwinding element, an AT rich region and one or more auxilliary sites for binding of transcription factors. The targets of the yeast mating type silencer proteins are also auxilliary sites of an origin of replication.

Interpretations

• An origin of DNA replication is a complex region of DNA, conceptually divisible into subregions.
• Some subregions are essential for origin activity. Others merely make initiation at that origin more efficient.
• Partial unwinding of the double helix appears necessary here, as in other cases.
• Transcription and its regulation may play a role in origin activity.

Further information

• DUE sequences are inherently easily melted.
• The protein-DNA interaction at the ORE is being investigated.

This is page 1325 of Molecular Genetics by Ulrich Melcher, © 1998