Genetic Control of the Cell-Division Cycle in Yeast, I. Detection of Mutants

Abstract

Abstract. Time-lapse photomicroscopy has been utilized to detect temperature-sensitive yeast mutants that are defective in gene functions needed at specific stages of the cell-division cycle. This technique provides two types of information about a mutant: the time at which the defective gene function is normally performed, defined as the execution point, and the stage at which cells collect when the function is not performed, defined as the termination point.Mutants carrying lesions in three genes that control the cell-division cycle are described. All three genes, cdc-1, cdc-2, and cdc-3, execute early in the cell cycle at about the time of bud initiation, but differ in their termination points. Cells carrying the cdc-1 mutation terminate at the execution point, most cells ending up with a tiny bud that does not develop further. Cells carrying the cdc-2 mutation terminate at mitosis. Cells carrying the cdc-3 mutation are defective in cell separation but show no definite termination point since other processes of the cell cycle, such as bud initiation and nuclear division, continue despite the block in cell separation.

A redox cycle within the cell cycle: ring in the old with the new

“…The tightly regulated progression through the cell cycle is brought about by periodic activation of cyclin and cyclindependent kinases (CDKs). The independent discoveries of cyclins in sea urchin oocytes, along with the simultaneous identification of maturation-promoting factors in frog oocytes and of CDC proteins in Saccharomyces cerevisiae, converged to give rise to the present-day concepts of cyclin-CDK complexes (Hartwell et al, 1970;Masui and Markert, 1971;Evans et al, 1983). The seminal discovery of cyclin/CDK complexes is believed to be at the core of understanding cellular proliferation controls.…”

SDC25, a dispensable Ras guanine nucleotide exchange factor of Saccharomyces cerevisiae differs from CDC25 by its regulation.

“…In the yeast S. cerevisiae, although SDC25 and CDC25 are two related genes, the CDC25 gene product appears to be the determinant GEF for growth because mutations lead to a Gl arrest (Hartwell et al, 1973). The SDC25 gene is dispensable under usual growth conditions and the absence of a detectable phenotype associated with deletion of the gene did not reveal its biological function (Damak et al, 1991).…”

A Survey of Essential Gene Function in the Yeast Cell Division Cycle

“…A very similar series of events occurs in all eukaryotes, with the obvious exception of bud emergence. Because of the fundamental biological importance of cell cycle progression and its importance in both human development and diseases such as cancer, identification of the molecular determinants of specific stages of the eukaryotic cell cycle has been a subject of intense study for several decades.The morphological landmarks of the cell cycle stages in budding yeast, most notably the size of the bud relative to the size of the mother cell, allows the identification of mutants blocked at specific stages of the cell cycle and thereby forms the basis for the classic cell cycle screens (Hartwell et al, 1970;Culotti and Hartwell, 1971;Hartwell, 1971aHartwell, , 1971bHartwell, , 1973Moir et al, 1982). These genetic screens, using conditional temperature-sensitive mutants, identified more than 50 genes that are required for specific stages in the cell division cycle and so were termed CDC genes.…”