KAR1/YNL188W Summary Help

Standard Name KAR1 1
Systematic Name YNL188W
Feature Type ORF, Verified
Description Protein involved in karyogamy and spindle pole body duplication; involved in karyogamy during mating; involved in spindle pole body duplication during mitosis; localizes to the half-bridge of the spindle pole body; interacts with Spc72p during karyogamy; also interacts with Cdc31p; essential gene (2, 3 and see Summary Paragraph)
Name Description KARyogamy 1
Chromosomal Location
ChrXIV:286308 to 287609 | ORF Map | GBrowse
Genetic position: -208 cM
Gene Ontology Annotations All KAR1 GO evidence and references
  View Computational GO annotations for KAR1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 2 genes
Classical genetics
reduction of function
Large-scale survey
reduction of function
39 total interaction(s) for 23 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 1
  • Affinity Capture-RNA: 1
  • Affinity Capture-Western: 3
  • Co-localization: 2
  • Protein-peptide: 1
  • Reconstituted Complex: 4
  • Two-hybrid: 4

Genetic Interactions
  • Dosage Lethality: 2
  • Dosage Rescue: 9
  • Phenotypic Enhancement: 1
  • Positive Genetic: 1
  • Synthetic Growth Defect: 4
  • Synthetic Lethality: 2
  • Synthetic Rescue: 4

Expression Summary
Length (a.a.) 433
Molecular Weight (Da) 50,653
Isoelectric Point (pI) 10.09
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXIV:286308 to 287609 | ORF Map | GBrowse
Genetic position: -208 cM
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1302 286308..287609 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000005132

KAR1 has been shown to be required for both mitosis and conjugation (4). KAR1 was first isolated in a screen for mutations that block karyogamy (1). There are two basic steps in the process of karyogamy: nuclear congression and nuclear fusion (5). While the cell membranes of two cells fuse in response to mating pheromone, microtubules form to connect the two nuclei. The nuclei move toward one another; the spindle pole bodies (SPB) then fuse, followed by nuclear membrane fusion (5).

In kar1 mutant zygotes, nuclei remain separated by 3.3 microns, never becoming close enough to fuse (5). Temperature-sensitive kar1 mutants also exhibit a block in the initial stage of SPB duplication (4). Kar1p is associated with the half bridge of the SPB and is involved in localizing other proteins, including Cdc31p, Cik1p, and Kar3p, to the SPB (2, 6, 5). Separate protein domains of Kar1p are required for its role in karyogamy and SPB duplication (7, 8, 5). An internal 70 amino acid region is necessary and sufficient to localize a Kar1p-beta-galactosidase fusion protein to the SPB, and deletions in this region disrupt SPB duplication but do not cause defects in nuclear fusion. The amino terminal region is required only for nuclear fusion, while the carboxy terminal region functions in both SPB duplication as well as nuclear fusion and localizes the protein to the nuclear envelope (8). There is an excellent review by Marsh and Rose (5) describing cell and nuclear fusion during mating.

Last updated: 2000-04-07 Contact SGD

References cited on this page View Complete Literature Guide for KAR1
1) Conde J and Fink GR  (1976) A mutant of Saccharomyces cerevisiae defective for nuclear fusion. Proc Natl Acad Sci U S A 73(10):3651-5
2) Spang A, et al.  (1995) The Cdc31p-binding protein Kar1p is a component of the half bridge of the yeast spindle pole body. J Cell Biol 128(5):863-77
3) Pereira G, et al.  (1999) Interaction of the yeast gamma-tubulin complex-binding protein Spc72p with Kar1p is essential for microtubule function during karyogamy. EMBO J 18(15):4180-95
4) Rose MD and Fink GR  (1987) KAR1, a gene required for function of both intranuclear and extranuclear microtubules in yeast. Cell 48(6):1047-60
5) Marsh L and Rose MD  (1997) "The pathway of cell and nuclear fusion during mating in S. cerevisiae" Pp. 827-888 in The Molecular and Cellular Biology of the Yeast Saccharomyces: Cell Cycle and Cell Biology, edited by Pringle JR, Broach JR and Jones EW. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press
6) Biggins S and Rose MD  (1994) Direct interaction between yeast spindle pole body components: Kar1p is required for Cdc31p localization to the spindle pole body. J Cell Biol 125(4):843-52
7) Vallen EA, et al.  (1992) Asymmetric mitotic segregation of the yeast spindle pole body. Cell 69(3):505-15
8) Vallen EA, et al.  (1992) Separate domains of KAR1 mediate distinct functions in mitosis and nuclear fusion. J Cell Biol 117(6):1277-87