Sorbose-utilizing Mutants Monosomic for Ch5
The loss and gain of one homolog
of a chromosome represents a novel
form of gene regulation.
Detailed studies of sorbose-utilizing mutants monosomic for Ch5 provided an understanding of some aspects of the mechanism of regulation as based on diminution of chromosome copy number. Ch5 monosomy and re-duplication occur at high frequencies with a high degree of fidelity, which fulfills a requirement for regulatory systems. Ch5 monosomy induces expression of the metabolic gene for sorbose catabolism, SOU1, which is carried on Ch4. The loss of an entire Ch5 is required because Ch5 carries multiple functionally redundant genes for the negative regulators of sorbose utilization that are scattered along the chromosome. Overall, we have suggested that the mode of gene regulation involving large genome rearrangements implies that regulatory and metabolic genes in C. albicans are distributed non-randomly over the chromosomes. An entire chromosome thus, can act as a single regulatory unit, a feature not previously considered.
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