High impact information on KAR1

• We suggest that KAR1 is anchored to the nuclear envelope and interacts with at least one other SPB component during the cell cycle [1].
• KAR1, a gene required for function of both intranuclear and extranuclear microtubules in yeast [2].
• Molecular analysis of the KAR1 gene of yeast has shown that it is required for both mitosis and conjugation [2].
• We conclude from our results that the KAR1, CDC28, and CDC37 gene products can diffuse between nuclei in a heterocaryon and that they probably perform their function for caryogamy prior to cell fusion [3].
• The kar1, cdc28, and cdc37 caryogamy defects are all phenotypically suppressed in this experiment (cdc4 could not be tested) [3].

Biological context of KAR1

• However, the CDC31 alleles also made the cell supersensitive to KAR1 gene dosage, arguing against a simple bypass mechanism of suppression [4].
• Suppressors of a kar1 allele defective for SPB duplication were isolated in two genes, CDC31 and DSK2 (Vallen, E.A., W.H., M. Winey, and M.D. Rose. 1994. Genetics. 137:407-422) [5].
• To identify interacting SPB proteins, we isolated 13 dominant mutations and 3 high copy number plasmids that suppressed the temperature sensitivity of kar1-delta 17 [4].
• KAR1 has been identified as an essential gene which is involved in karyogamy of mating yeast cells and in spindle pole body duplication of mitotic cells (Rose, M. D., and G. R. Fink. 1987. Cell. 48:1047-1060) [6].
• Kar1p is associated with the spindle pole body during the entire cell cycle of yeast [6].

Anatomical context of KAR1

• KAR1 is required for duplication of the Saccharomyces cerevisiae microtubule organizing center, the spindle pole body (SPB) (Rose, M.D., and G.R. Fink, 1987. Cell. 48:1047-1060) [5].
• In the spheroplast fusion system, nuclear fusion is dependent on both the KAR1 gene and prior exposure to alpha factor [7].

Associations of KAR1 with chemical compounds

• Transfer of genes for utilization of starch (sta2) and melibiose (mel) to industrial strains of Saccharomyces cerevisiae by single-chromosome transfer, using a kar1 mutant as vector [8].

Physical interactions of KAR1

• Using a protein blotting technique, Cdc31p bound to Kar1p in vitro via an essential domain in Kar1p required for SPB duplication (Vallen, E. A., M. A. Hiller, T. Y. Scherson, and M. D. Rose. 1992a. J. Cell Biol. 117:1277-1287) [9].
• Binding of centrins and yeast calmodulin to synthetic peptides corresponding to binding sites in the spindle pole body components Kar1p and Spc110p [10].

Other interactions of KAR1

• The Saccharomyces cerevisiae genes KAR1 and CDC31 are required for the initial stages of spindle pole body (SPB) duplication in yeast [9].
• Interaction of the yeast gamma-tubulin complex-binding protein Spc72p with Kar1p is essential for microtubule function during karyogamy [11].
• In addition, we found that Bbp1p interacts with Spc29p and the half-bridge component Kar1p [12].
• Both functions of Nud1p are connected to the ability of Spc72p to bind to the outer plaque and half-bridge (via Kar1p) of the SPB [13].
• By utilizing the Kar1(299)-Gal4 construct, we isolated ten spontaneous mutations that were defective in the Kar1-Gal4p localization [14].

Analytical, diagnostic and therapeutic context of KAR1

• The Kar1 protein, a component of the yeast spindle pole body (SPB), was shown to be targeted to the SPB by electron microscopic analysis, or indirect immunofluorescence methods [14].
• Titration of a peptide fragment from the yeast Kar1p protein to the isolated domains and intact caltractin shows that the two domains interact in a Ca2+-dependent manner, with the C-terminal domain binding much more strongly than the N-terminal domain [15].

References