We have isolated a fourth myosin gene (MYO4) in yeast (Saccharomyces cerevisiae). MYO4 encodes a approximately 170 kDa (1471 amino acid) class V myosin, using the classification devised by Cheney et al. (1993a; Cell Motil. Cytoskel. 24, 215–223); the motor domain is followed by a neck region containing six putative calmodulin-binding sites and a tail with a short potential ‘coiled-coil’ domain. A comparison with other myosins in GenBank reveals that Myo4 protein is most closely related to the yeast Myo2 protein, another class V myosin. Deletion of MYO4 produces no detectable phenotype, either alone or in conjunction with mutations in myo2 or other myosin genes, the actin gene, or secretory genes. However, overexpression of MYO4 or MYO2 results in several morphological abnormalities, including the formation of short strings of unseparated cells in diploid strains, or clusters of cells in haploid strains. Alterations of MYO4 or MYO2 indicate that neither the motor domains nor tails of these myosins are required to confer the overexpression phenotype, whereas the neck region may be required. Although this phenotype is similar to that seen upon MYO1 deletion, we provide evidence that the overexpression of Myo4p or Myo2p is not simply interfering with Myo1p function.

Cheney
R. E.
,
Mooseker
M. S.
(
1992
).
Unconventional myosins.
Curr. Opin. Cell Biol
4
,
27
35
Cheney
R. E.
,
Riley
M. A.
,
Mooseker
M. S.
(
1993
).
Phylogenetic analysis of the myosin superfamily.
Cell Motil. Cytoskel
24
,
215
223
Cheney
R. E.
,
O'Shea
M. K.
,
Heuser
J. E.
,
Coelho
M. V.
,
Wolenski
J. S.
,
Espreafico
E. M.
,
Forscher
P.
,
Larson
R. E.
,
Mooseker
M. S.
(
1993
).
Brain myosin-V is a two-headed unconventional myosin with motor activity.
Cell
75
,
13
23
Cohen
C.
,
Parry
D. A. D.
(
1990
).
-helical coiled coils and bundles: how to design an -helical protein.
Proteins
7
,
1
15
Davis
T. N.
(
1992
).
A temperature-sensitive calmodulin mutant loses viability during mitosis.
J. Cell Biol
118
,
607
617
Devereux
J.
,
Haeberli
P.
,
Smithies
O.
(
1984
).
A comprehensive set of sequence analysis programs for the VAX.
Nucl. Acids Res
12
,
387
395
Diehl
B. E.
,
Pringle
J. R.
(
1991
).
Molecular analysis of Saccharomyces cerevisiae chromosome I: identification of additional transcribed regions and demonstration that some encode essential functions.
Genetics
127
,
287
298
Espindola
F. S.
,
Espreafico
E. M.
,
Coelho
M. V.
,
Martins
A. R.
,
Costa
F. R.
,
Mooseker
M. S.
,
Larson
R. E.
(
1992
).
Biochemical and immunological characterization of p190-calmodulin complex from vertebrate brain: a novel calmodulin-binding myosin.
J. Cell Biol
118
,
359
368
Espreafico
E. M.
,
Cheney
R. E.
,
Matteoli
M.
,
Nascimento
A. A. C.
,
De Camilli
P. V.
,
Larson
R. E.
,
Mooseker
M. S.
(
1992
).
Primary structure and cellular localization of chicken brain myosin-V (p190), an unconventional myosin with calmodulin light chains.
J. Cell Biol
119
,
1541
1557
Feinberg
A. P.
,
Vogelstein
B.
(
1983
).
A technique for radiolabeling DNA restriction endonuclease fragments to high specific activity.
Anal. Biochem
132
,
6
13
Gerst
J. E.
,
Rodgers
L.
,
Riggs
M.
,
Wigler
M.
(
1992
).
SNC1, a yeast homolog of the synaptic vesicle-associated membrane protein/ synaptobrevin gene family: genetic interactions with the RAS and CAP genes.
Proc. Nat. Acad. Sci. USA
89
,
4338
4342
Goodson
H. V.
,
Titus
M. A.
,
Spudich
J. A.
(
1990
).
Disruption of a yeast unconventional myosin.
J. Cell Biol
111
,
168
–.
Govindan
B.
,
Bowser
R.
,
Novick
P.
(
1991
).
Role of the unconventional myosin gene MYO2 in the yeast secretory pathway.
J. Cell Biol
115
,
185
–.
Haarer
B. K.
,
Pringle
J. R.
(
1987
).
Immunofluorescence localization of the Saccharomyces cerevisiaeCDC12 gene product to the vicinity of the 10-nm filaments in the mother-bud neck.
Mol. Cell. Biol
7
,
3678
3687
Haarer
B. K.
,
Lillie
S. H.
,
Adams
A. E.
,
Magdolen
V.
,
Bandlow
W.
,
Brown
S. S.
(
1990
).
Purification of profilin from Saccharomyces cerevisiae and analysis of profilin-deficient cells.
J. Cell Biol
110
,
105
114
Hicks
J. B.
,
Strathern
J. N.
,
Herskowitz
I.
(
1977
).
Interconversion of yeast mating types III. Action of homothalism (HO) gene in cells homozygous for the mating type locus.
Genetics
85
,
395
405
Hill
J. E.
,
Myers
A. M.
,
Koerner
T. J.
,
Tzagoloff
A.
(
1986
).
Yeast/ E. coli shuttle vectors with multiple unique restriction sites.
Yeast
2
,
163
167
Johnston
G. C.
,
Prendergast
J. A.
,
Singer
R. A.
(
1991
).
The Saccharomyces cerevisiaeMYO2 gene encodes an essential myosin for vectorial transport of vesicles.
J. Cell Biol
113
,
539
551
Kim
H. B.
,
Haarer
B. K.
,
Pringle
J. R.
(
1991
).
Cellular morphogenesis in the Saccharomyces cerevisiae cell cycle: localization of the CDC3 gene product and the timing of events at the budding site.
J. Cell Biol
112
,
535
544
Larson
R. E.
,
Pitta
D. E.
,
Ferro
J. A.
(
1988
).
A novel 190 kDa calmodulin-binding protein associated with brain actomyosin.
Brazilian J. Med. Biol. Res
21
,
213
217
Lillie
S. H.
,
Pringle
J. R.
(
1980
).
Reserve carbohydrate metabolism in Saccharomyces cerevisiae: responses to nutrient limitation.
J. Bacteriol
143
,
1384
1394
Lillie
S. H.
,
Brown
S. S.
(
1992
).
Suppression of a myosin defect by a kinesin-related gene.
Nature
356
,
358
361
Lupas
A.
,
Van Dyke
M.
,
Stock
J.
(
1991
).
Predicting coiled coils from protein sequences.
Science
252
,
1162
1164
Mercer
J. A.
,
Seperack
P. K.
,
Strobel
M. C.
,
Copeland
N. G.
,
Jenkins
N. A.
(
1991
).
Novel myosin heavy chain encoded by murine dilute coat colour locus (see correction Nature 352, 547).
Nature
349
,
709
712
Pringle
J. R.
,
Adams
A. E. M.
,
Drubin
D. G.
,
Haarer
B. K.
(
1991
).
Immunofluorescence methods for yeast.
Meth. Enzymol
194
,
565
602
Rayment
I.
,
Rypniewski
W. R.
,
Schmidt-Base
K.
,
Smith
R.
,
Tomchick
D. R.
,
Benning
M. M.
,
Winkelmann
D. A.
,
Wesenberg
G.
,
Holden
H. M.
(
1993
).
Three-dimensional structure of myosin subfragment-1: a molecular motor.
Science
261
,
50
58
Roberts
C. J.
,
Raymond
C. K.
,
Yamashiro
C. T.
,
Stevens
T. H.
(
1991
).
Methods for studying the yeast vacuole.
Meth. Enzymol
194
,
644
661
Rodriguez
J. R.
,
Paterson
B. M.
(
1990
).
Yeast myosin heavy chain mutant: maintenance of the cell type specific budding pattern and the normal deposition of chitin and cell wall components requires an intact myosin heavy chain gene.
Cell Motil. Cytoskel
17
,
301
308
Rose
M. D.
,
Novick
P.
,
Thomas
J. H.
,
Botstein
D.
,
Fink
G. R.
(
1987
).
A Saccharomyces cerevisiae genomic plasmid bank based on a centromere-containing shuttle vector.
Gene
60
,
237
243
Rothstein
R. J.
(
1983
).
One-step gene disruption in yeast.
Meth. Enzymol
101
,
202
211
Ruther
U.
,
Muller-Hill
B.
(
1983
).
Easy identification of cDNA clones.
EMBO J
2
,
1791
1794
Sanger
F.
,
Nicklin
S.
,
Coulson
A. R.
(
1977
).
DNA sequencing with chain-terminating inhibitors.
Proc. Nat. Acad. Sci. USA
74
,
5463
5467
Sloat
B. F.
,
Adams
A.
,
Pringle
J. R.
(
1981
).
Roles of the CDC24 gene product in cellular morphogenesis during the Saccharomyces cerevisiae cell cycle.
J. Cell Biol
89
,
395
405
Watts
F. Z.
,
Shiels
G.
,
Orr
E.
(
1987
).
The yeast MYO1 gene encoding a myosin-like protein required for cell division.
EMBO J
6
,
3499
3505
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