The p34cdc2 kinase is essential for progression past Start in the G1 phase of the fission yeast cell cycle, and also acts in G2 to promote mitotic entry. Whilst very little is known about the G1 function of cdc2, the rum1 gene has recently been shown to encode an important regulator of Start in fission yeast, and a model for rum1 function suggests that it inhibits p34cdc2 activity. Here we present genetic data suggesting that rum1 maintains p34cdc2 in a pre-Start G1 form, inhibiting its activity until the cell achieves the critical mass required for Start, and find that in the absence of rum1 p34cdc2 has increased Start activity in vivo. It is also known that mutation of cdc2, or overexpression of rum1, can disrupt the dependency of S-phase upon mitosis, resulting in an extra round of S-phase in the absence of mitosis. We show that cdc2 and rum1 interact in this process, and describe dominant cdc2 mutants causing multiple rounds of S-phase in the absence of mitosis. We suggest that interaction of rum1 and cdc2 regulates Start, and this interaction is important for the regulation of S-phase within the cell cycle.

REFERENCES

Adolph
S.
,
Brusselbach
S.
,
Muller
R.
(
1993
).
Inhibition of transcription blocks cell cycle progression of NIH3T3 fibroblasts specifically in G1.
J. Cell Sci
105
,
113
122
Basi
G.
,
Schmid
E.
,
Maundrell
K.
(
1993
).
TATA box mutations in the Schizosaccharomyces pombe nmt1 promoter affect transcription efficiency but not the transcription start point or thiamine repressibility.
Gene
123
,
131
136
Booher
R. N.
,
Alfa
C. E.
,
Hyams
J. S.
,
Beach
D. H.
(
1989
).
The fission yeast cdc2/cdc13/suc1 protein kinase: regulation of catalytic activity and nuclear localization.
Cell
58
,
485
497
Broek
D.
,
Bartlett
R.
,
Crawford
K.
,
Nurse
P.
(
1991
).
Involvement of p34 cdc2 in establishing the dependency of S phase on mitosis.
Nature
349
,
388
93
Bueno
A.
,
Richardson
H.
,
Reed
S. I.
,
Russell
P.
(
1991
).
A fission yeast B-type cyclin functioning early in the cell cycle.
Cell
66
,
149
159
Bueno
A.
,
Russell
P.
(
1993
).
Two fission yeast B-type cyclins, cig2 and cdc13, have different functions in mitosis.
Mol. Cell Biol
13
,
2286
2297
Caligiuri
M.
,
Beach
D.
(
1993
).
Sct1 functions in partnership with cdc10 in a transcriptional complex that activates cell cycle ‘start’ and inhibits differentiation.
Cell
72
,
607
619
Carr
A. M.
,
MacNeill
S. A.
,
Hayles
J.
,
Nurse
P.
(
1989
).
Molecular cloning and sequence analysis of mutant alleles of the fission yeast cdc2 protein kinase gene: implications for cdc2+protein structure and function.
Mol. Gen. Genet
218
,
41
49
Connolly
T.
,
Beach
D.
(
1994
).
Interaction between the Cig1 and Cig2 B-type cyclins in the fission yeast cell cycle.
Mol. Cell Biol
14
,
768
776
Creanor
J.
,
Mitchison
J. M.
(
1994
).
The kinetics of H1 histone kinaseactivation during the cell cycle of wild-type and wee mutants of the fission yeast Schizosaccharomyces pombe.
J. Cell Sci
107
,
1197
1204
Dulic
V.
,
Kaufmann
W. K.
,
Wilson
S. J.
,
Tlsty
T. D.
,
Lees
E.
,
Harper
J. W.
,
Elledge
S. J.
,
Reed
S. I.
(
1994
).
p53-Dependent inhibition of cyclin-dependent kinase activities in human fibroblasts during radiation-induced G1arrest.
Cell
76
,
1013
1023
El-Deiry
W. S.
,
Tokino
T.
,
Velculescu
V. E.
,
Levy
D. B.
,
Parsons
R.
,
Trent
J. M.
,
Lin
D.
,
Mercer
W. E.
,
Kinzler
K. W.
,
Vogelstein
B.
(
1993
).
WAF1, a potential mediator of p53 tumor suppression.
Cell
75
,
817
825
Endicott
J. A.
,
Nurse
P.
,
Johnson
L. N.
(
1994
).
Mutational analysis supports a structural model for the cell cycle protein kinase p34.
Prot. Eng
7
,
243
253
Fleig
U.
,
Nurse
P.
(
1991
).
Expression of a dominant negative allele of cdc2 prevents activation of the endogenous p34 cdc2 kinase.
Mol.Gen. Genet
226
,
432
440
Fleig
U. N.
,
Gould
K. L.
,
Nurse
P.
(
1992
).
A dominant negative allele of p34 cdc2 shows altered phosphoamino acid content and sequesters p56 cdc13 cyclin.
Mol. Cell Biol
12
,
2295
2301
Forsburg
S. L.
,
Nurse
P.
(
1991
).
Identification of a G1-type cyclin puc1+ in the fission yeast Schizosaccharomyces pombe.
Nature
351
,
245
8
Forsburg
S. L.
,
Nurse
P.
(
1994
).
Analysis of the Schizosaccharomyces pombe cyclin puc1: evidence for a role in cell cycle exit.
J. Cell Sci
107
,
601
613
Hanks
S. K.
,
Quinn
A. M.
,
Hunter
T.
(
1988
).
The protein kinase family: conserved features and deduced phylogeny of the catalytic domains.
Science
241
,
42
52
Hartwell
L.
(
1974
).
Saccharomyces cerevisiae cell cycle.
Bacteriol. Rev.
,
38
,
164
198
Hayles
J.
,
Fisher
D.
,
Woolard
A.
,
Nurse
P.
(
1994
).
Temporal order of S phase and mitosis in fission yeast is determined by the state of the p34 cdc2 -mitotic B cyclin complex.
Cell
78
,
813
822
Hayles
J.
,
Nurse
P.
(
1995
).
A pre-start checkpoint preventing mitosis in fission yeast acts independently of p34cdc2tyrosine phosphorylation.
EMBO J
14
,
2760
2771
Hofer
F.
,
Hollerstein
H.
,
Janner
F.
,
Minet
M.
,
Thuriaux
P.
,
Leupold
U.
(
1979
).
The genetic fine structure of nonsense suppressors in Schizosaccharomyces pombe.
Curr. Genet
1
,
45
61
Hunter
T.
(
1993
).
Braking the cycle.
Cell
75
,
839
841
Knighton
D. R.
,
Zheng
J.
,
Eyck
L. F. T.
,
Xuong
N.
,
Taylor
S. S.
,
Sowadski
J. M.
(
1991
).
Structure of a peptide inhibitor bound to the catalytic subunit of cyclic adenosine monophosphate-dependent protein kinase.
Science
253
,
414
420
Labib
K.
,
Craven
R.
,
Crawford
K.
,
Nurse
P.
(
1995
).
Dominant mutants identify new roles for p34 cdc2 in mitosis.
EMBO J
14
,
2155
2165
Lamb
A.
,
Gruis
N. A.
,
Weaver-Feldhaus
J.
,
Liu
Q.
,
Harshman
K.
,
Tavtigian
S. V.
,
Stockert
E.
,
Day
R. S.
III
,
Johnson
B. E.
,
Skolnick
M. H.
(
1994
).
A cell cycle regulator potentially involved in genesis of many tumor types.
Science
264
,
436
440
Lowndes
N. F.
,
McInerny
C. J.
,
Johnson
A. L.
,
Fantes
P. A.
,
Johnson
L. H.
(
1992
).
Control of DNA synthesis genes in fission yeast by the cell cycle gene cdc10+.
Nature
355
,
449
53
MacNeill
S.
,
Nurse
P.
(
1993
).
Mutational analysis of the fission yeast p34 cdc2 protein kinase gene.
Mol. Gen. Genet.
,
236
,
415
426
Marcote
M. J.
,
Knighton
D. R.
,
Basi
G.
,
Sowadski
J. M.
,
Brambilla
P.
,
Draetta
G.
,
Taylor
S. S.
(
1993
).
A three-dimensional model of the Cdc2 protein kinase: localization of cyclin-and Suc1-binding regions and phosphorylation sites.
Mol. Cell Biol
13
,
5122
5131
Maundrell
K.
(
1993
).
Thiamine-repressible expression vectors pREP and pRIP for fission yeast.
Gene
123
,
127
130
Mendenhall
M. D.
,
Richardson
H. E.
,
Reed
S. I.
(
1988
).
Dominant negative protein kinase mutations that confer a G1arrest phenotype.
Proc. Nat. Acad. Sci. USA
85
,
4426
4430
Moreno
S.
,
Hayles
J.
,
Nurse
P.
(
1989
).
Regulation of p34 cdc2 protein kinase during mitosis.
Cell
58
,
361
372
Moreno
S.
,
Klar
A.
,
Nurse
P.
(
1991
).
Molecular genetic analysis of fission yeast Schizosaccharomyces pombe.
Meth. Enzymol
194
,
795
23
Moreno
S.
,
Nurse
P.
(
1994
).
Regulation of progression through the G1phase of the cell cycle by the rum1+ gene.
Nature
367
,
236
242
Nasmyth
K.
,
Nurse
P.
,
Fraser
R.
(
1979
).
The effect of cell mass on the cell cycle timing and duration of S-phase in fission yeast.
J. Cell Sci
39
,
215
233
Nasmyth
K.
,
Hunt
T.
(
1993
).
Dams and sluices.
Nature
366
,
634
635
Nobori
T.
,
Miura
K.
,
Wu
D. J.
,
Lois
A.
,
Takabayashi
K.
,
Carson
D.A.
(
1994
).
Deletions of the cyclin-dependent kinase-4 inhibitor gene in multiple human cancers.
Nature
368
,
753
756
Nurse
P.
,
Thuriaux
P.
(
1977
).
Controls over the timing of DNA replication during the cell cycle of fission yeast.
Exp. Cell Res
107
,
365
75
Nurse
P.
,
Bissett
Y.
(
1981
).
Gene required in Glfor commitment to cell cycle and in G2for control of mitosis in fission yeast.
Nature
292
,
558
560
Obara-Ishihara
T.
,
Okayama
H.
(
1994
).
A B-type cyclin negatively regulates conjugation via interacting with cell cycle ‘start’ genes in fission yeast.
EMBO J
13
,
1863
1872
Okazaki
K.
,
Okazaki
N.
,
Kume
K.
,
Jinno
S.
,
Tanaka
K.
,
Okayama
H.
(
1990
).
High efficiency transformation method and library transducing vectors for cloning mammalian cDNAs by trans-complementation of Schizosaccharomyces pombe.
Nucl. Acids Res
18
,
6485
6489
Pines
J.
(
1994
).
p21 inhibits cyclin shock.
Nature
369
,
520
521
Reymond
A.
,
Marks
J.
,
Simanis
V.
(
1993
).
The activity of S. pombe DSC1-like factor is cell cycle regulated and dependent on the activity of p34 cdc2.
EMBO J
12
,
4325
4334
Sazer
S.
,
Sherwood
S. W.
(
1990
).
Mitochondrial growth and DNA synthesis occur in the absence of nuclear DNA replication in fission yeast.
J. Cell Sci
97
,
509
516
Schwob
E.
,
Bohm
T.
,
Mendenhall
M.
,
Nasmyth
K.
(
1994
).
The B-type cyclin kinase inhibitor p40 SIC1 controls the G1to S transition in S. cerevisiae.
Cell
79
,
233
244
Sherr
C. J.
(
1993
).
Mammalian G1cyclins.
Cell
73
,
1059
1065
Tanaka
K.
,
Okazaki
K.
,
Okazaki
N.
,
Ueda
T.
,
Sugiyama
A.
,
Nojima
H.
,
Okayama
H.
(
1992
).
A new cdc -gene required for S-phase entry of Schizosaccharomyces-pombe encodes a protein similar to the cdc10+ and swi4 -gene products.
EMBO J
11
,
4923
4932
Usui
T.
,
Yoshida
M.
,
Abe
K.
,
Osada
H.
,
Isono
K.
,
Beppu
T.
(
1991
).
Uncoupled cell cycle without mitosis induced by a protein kinase inhibitor, K-252a.
J. Cell Biol
115
,
1275
1282
Van den Heuvel
S.
,
Harlow
E.
(
1993
).
Distinct roles for cyclin-dependent kinases in cell cycle control.
Science
262
,
2050
2054
Waga
S.
,
Hannon
G. J.
,
Beach
D.
,
Stillman
B.
(
1994
).
The p21 inhibitor of cyclin-dependent kinases controls DNA replication by interaction with PCNA.
Nature
369
,
574
578
Woods
A.
,
Sherwin
T.
,
Sasse
R.
,
McRae
T.
,
Baines
A.
,
Gull
K.
(
1989
).
Definition of individual components within the cytoskeleton of Trypanosoma brucei by a library of monoclonal antibodies.
J. Cell Sci
93
,
491
500
Yoshida
M.
,
Nishikawa
M.
,
Nishi
K.
,
Abe
K.
,
Horinouchi
S.
,
Beppu
T.
(
1990
).
Effects of leptomycin B on the cell cycle of fibroblasts and fission yeast cells.
Exp. Cell Res
187
,
150
6
This content is only available via PDF.