NDC1: a nuclear periphery component required for yeast spindle pole body duplication.
The spindle pole body (SPB) of Saccharomyces cerevisiae serves as the centrosome in this organism, undergoing duplication early in the cell cycle to generate the two poles of the mitotic spindle. The conditional lethal mutation ndc1-1 has previously been shown to cause asymmetric segregation, wherein all the chromosomes go to one pole of the mitotic spindle (Thomas, J. H., and D. Botstein. 1986. Cell. 44:65-76). Examination by electron microscopy of mutant cells subjected to the nonpermissive temperature reveals a defect in SPB duplication. Although duplication is seen to occur, the nascent SPB fails to undergo insertion into the nuclear envelope. The parental SPB remains functional, organizing a monopolar spindle to which all the chromosomes are presumably attached. Order-of-function experiments reveal that the NDC1 function is required in G1 after alpha-factor arrest but before the arrest caused by cdc34. Molecular analysis shows that the NDC1 gene is essential and that it encodes a 656 amino acid protein (74 kD) with six or seven putative transmembrane domains. This evidence for membrane association is further supported by immunofluorescent localization of the NDC1 product to the vicinity of the nuclear envelope. These findings suggest that the NDC1 protein acts within the nuclear envelope to mediate insertion of the nascent SPB.
Winey
M
M
Department of Molecular, Cellular, and Developmental Biology, University of Colorado-Boulder 80309-0347.
Hoyt
M A
MA
Chan
C
C
Goetsch
L
L
Botstein
D
D
Byers
B
B
D000595:Amino Acid Sequence; D001483:Base Sequence; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000378:metabolism*; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009685:Nuclear Envelope / Q000648:ultrastructure*; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins / Q000378:metabolism*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D008941:Spindle Apparatus / Q000648:ultrastructure*
D005656:Fungal Proteins; D008565:Membrane Proteins; C082594:NDC1 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins