The SAC3 gene of Saccharomyces serevisiae has been implicated in actin function by genetic experiments showing that a temperature sensitive mutation in the essential actin gene (actl-1) can be suppressed by mutations in SAC3. An involvement of SAC3 in actin function is further suggested by the observation that the actin cytoskeleton is altered in SAC3 mutants. Our fractionation experiments, however, point to a nuclear localization of Sac3p. On sucrose density gradients Sac3p co-fractionated with the nuclear organelle markers examined. Furthermore, Sac3p was enriched 10-fold in a nuclei preparation along with the nuclear protein Nop1p. In this report we further show that SAC3 function is required for normal progression of mitosis. SAC3 mutants showed a higher fraction of large-budded cells in culture, indicative of a cell cycle delay. The predominant population among the large-budded sac3 cells were cells with a single nucleus at the bud-neck and a short intranuclear spindle. This suggests that a cell cycle delay occurs in mitosis prior to anaphase. The observation that SAC3 mutants lose chromosomes with higher frequency than wild-type is another indication for a mitotic defect in SAC3 mutants. We further noticed that SAC3 mutants are more resistant against the microtubule destabilizing drug benomyl. This finding suggests that SAC3 is involved, directly or indirectly, in microtubule function. In summary, our data indicate that SAC3 is involved in a process which affects both the actin cytoskeleton and mitosis.

REFERENCES

Amati
B. B.
,
Gasser
S. M.
(
1988
).
Chromosomal ARS and CEN elements bind specifically to the yeast nuclear scaffold.
Cell
54
,
967
978
Brown
M. T.
,
Goetsch
L.
,
Hartwell
L. H.
(
1993
).
MIF2 is required for mitotic spindle integrity during anaphase spindle elongation in Saccharomyces cerevisiae.
J. Cell Biol
123
,
387
403
Christianson
T. W.
,
Sikorski
R. S.
,
Dante
M.
,
Shero
J. H.
,
Hieter
P.
(
1992
).
Multifunctional yeast high-copy-number shuttle vectors.
Gene
110
,
119
122
Clark
M. W.
,
Yip
M. L. R.
,
Campbell
J.
,
Abelson
J.
(
1990
).
SSB-1 of the yeast Saccharomyces cerevisiae is a nucleolar-specific, silver-binding protein that is associated with the snR10 and snR11 small nuclear RNAs.
J. Cell Biol
111
,
1741
1751
Dieckmann
C. L.
,
Tzagoloff
A.
(
1985
).
Assembly of the mitochondrial membrane system. CBP6, a yeast nuclear gene necessary for the synthesis of cytochrome b.
J. Biol. Chem
260
,
1513
1520
Eshel
D.
,
Urrestarazu
L. A.
,
Vissers
S.
,
Jauniaux
J.-C.
,
van Vliet-Reedijk
J. C.
,
Planta
R. J.
,
Gibbons
I. R.
(
1993
).
Cytoplasmic dynein is required for normal nuclear segregation in yeast.
Proc. Nat. Acad. Sci. USA
90
,
11172
11176
Gallwitz
D.
,
Seidel
R.
(
1980
).
Molecular cloning of the actin gene from yeast Saccharomyces cerevisiae.
Nucl. Acids Res
8
,
1043
1059
Hartwell
L. H.
,
Smith
D.
(
1985
).
Altered fidelity of mitotic chromosome transmission in cell cycle mutants of S. cerevisiae.
Genetics
110
,
381
395
Hoyt
M. A.
,
Totis
L.
,
Roberts
B. T.
(
1991
).
S. cerevisiae genes required for cell cycle arrest in response to loss of microtubule function.
Cell
66
,
507
517
Hurt
E. C.
,
McDowall
A.
,
Schimmang
T.
(
1988
).
Nucleolar and nuclear envelope proteins of the yeast Saccharomyces cerevisiae.
Eur. J. Cell Biol
46
,
554
563
Jacobs
C. W.
,
Adams
A. E. M.
,
Szaniszlo
P. J.
,
Pringle
J. R.
(
1988
).
Functions of microtubules in the Saccharomyces cerevisiae cell cycle.
J. Cell Biol
107
,
1409
1426
Julius
D.
,
Brake
A.
,
Blair
L.
,
Kunisawa
R.
,
Thorner
J.
(
1984
).
Isolation of the putative structural gene for the lysine-arginine-cleaving endopeptidase required for processing of yeast prepro-a-factor.
Cell
37
,
1075
1089
Kilmartin
J. V.
,
Wright
B.
,
Milstein
C.
(
1982
).
Rat monoclonal antitubulin antibodies derived by using a new non-secreting rat cell line.
J. Cell Biol
93
,
576
582
Kölling
R.
,
Hollenberg
C. P.
(
1994
).
The ABC-transporter Ste6 accumulates in the plasma membrane in a ubiquitinated form in endocytosis mutants.
EMBO J
13
,
3261
3271
Lew
D. J.
,
Reed
S. I.
(
1995
).
A cell cycle checkpoint monitors cell morphogenesis in budding yeast.
J. Cell Biol
129
,
739
749
Ma
H.
,
Kunes
S.
,
Schatz
P. J.
,
Botstein
D.
(
1987
).
Plasmid construction by homologous recombination in yeast.
Gene
58
,
201
216
Ng
R.
,
Abelson
J.
(
1980
).
Isolation and sequence of the gene for actin in Saccharomyces cerevisiae.
Proc. Nat. Acad. Sci. USA
77
,
3912
3916
Novick
P.
,
Botstein
D.
(
1985
).
Phenotypic analysis of temperature-sensitive yeast actin mutants.
Cell
40
,
405
416
Novick
P.
,
Osmond
B. C.
,
Botstein
D.
(
1989
).
Suppressors of yeast actin mutations.
Genetics
121
,
659
674
Osborne
M. A.
,
Schlenstedt
G.
,
Jinks
T.
,
Silver
P. A.
(
1994
).
Nuf2, a spindle pole body-associated protein required for nuclear division in yeast.
J. Cell Biol
125
,
853
866
Palmer
R. E.
,
Sullivan
D. S.
,
Huffaker
T.
,
Koshland
D.
(
1992
).
Role ofastral microtubules and actin in spindle orientation and migration in the budding yeast, Saccharomyces cerevisiae.
J. Cell Biol
119
,
583
593
Pringle
J. R.
,
Preston
R. A.
,
Adams
A. E. M.
,
Stearns
T.
,
Drubin
D. G.
,
Haarer
B. K.
,
Jones
E. W.
(
1989
).
Fluorescence microscopy methods for yeast.
Meth. Cell Biol
31
,
357
434
Roof
D. M.
,
Meluh
P. B.
,
Rose
M. D.
(
1992
).
Kinesin-related proteins required for assembly of the mitotic spindle.
J. Cell Biol
118
,
95
108
Schimmang
T.
,
Tollervey
D.
,
Kern
H.
,
Frank
R.
,
Hurt
E. C.
(
1989
).
A yeast nucleolar protein related to mammalian fibrillarin is associated with small nucleolar RNA and is essential.
EMBO J
8
,
4015
4024
Serrano
R.
,
Kielland-Brandt
M. C.
,
Fink
G. R.
(
1986
).
Yeast plasma membrane ATPase is essential for growth and has homology with (Na++ K+), K+-and Ca2+-ATPases.
Nature
319
,
689
693
Sullivan
D. S.
,
Huffaker
T. C.
(
1992
).
Astral microtubules are notrequired for anaphase B in Saccharomyces cerevisiae.
J. Cell Biol
119
,
379
388
Takeda
M.
,
Vassarotti
A.
,
Douglas
M. G.
(
1985
).
Nuclear genes coding the yeast mitochondrial adenosine triphosphatase complex. Primary sequence analysis of ATP2 encoding the F1-ATPase beta-subunit precursor.
J. Biol. Chem
260
,
15458
15465
Weinert
T. A.
,
Hartwell
L. H.
(
1988
).
The RAD9 gene controls the cell cycle response to DNA damage in Saccharomyces cerevisiae.
Science
241
,
317
322
Yoshihisa
T.
,
Anraku
Y.
(
1990
).
A novel pathway of import of-mannosidase, a marker enzyme of vacuolar membrane, in Saccharomyces cerevisiae.
J. Biol. Chem
265
,
22418
22424
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