Current Genetics 2, 75-78(1980)
~ ©
~ by Springer-Verlag 1980
Chromosomal Proteins in Saccharomyces cerevisiae II. C h r o m o s o m e D o s a g e E f f e c t on the Cellular a n d N u c l e a r C o n t e n t o f N o n h i s t o n e P r o t e i n s
Kay Gull6v and J6rgen Friis Department of Molecular Biology, University of Odense, Campusvej 55, DK-5230 Odense M., Denmark
Summary. The effect of varying the chromosomal dosage in aneuploids for chromosome I or VII on the synthesis of individual nonhistone proteins was revealed. The nuclear content of most nonhistone proteins seemed to be little impaired in a strain with tetrasomy for chromosome VII as compared with a strain which is disomic for chromosome VII. On the contrary, tetrasomy for chromosome I as compared with disomy for this chromosome seems to impair both the cellular and the nuclear content of a number of chromosomal proteins, including the tubulin subunits.
Key words: Aneuploid strains - Two-dimensional electrophoresis.
Introduction
These observations led to the suggestion that most or all of the rRNA cistrons in yeast were located on chromosome I. Genetic analysis, involving fusion of haploids with different EcoRI restriction patterns within the rDNA sequence, and subsequent spomlation, have revealed a segregation pattern consistent with the location of the rRNA genes within one linkage group (Petes et al., 1977). Contrary to the previous assumption, elaborate genetic analysis by Petes (1979) indicated that the rRNA genes are linked mitotically to chromosome XII. In view o f these observations we have investigated the gene dosage effect of two chromosomes including no. I on the number and amounts of individual nonhistone proteins in the yeast nucleus to see if the composition of yeast chromatin is specifically impaired.
Materials and Methods
Yeast strains aneuploid for chromosome I exhibit a peculiar adjustment pattern of the number of rRNA cistrons per genome. Saturation hybridization experiments with diploid strains with monosomy for chromo. some I, reveals that the hybridization level with rRNA is reduced approximately 35% (Finkelstein et al., 1972; 0 y e n , 1973; Kaback et al., 1973). Similarly, the hybridization level with rRNA in diploids, which are tetrasomic for chromosome I is increased by 5 0 - 6 0 % (Seligy and James, 1977). A diploid strain which is monosomic for chromosome I and initially deficient for 30% of the rRNA genes, when repeatedly subcultured, increased the number of rRNA genes to a stable level characteristic of a normal diploid (Kaback and Halvorson, 1977).
These strains are essentially homozygous and identical in their genetic background. All strains are derived from a homothallic spore clone, with tetrasomy for chromosome I and VII (Seligy and James, 1977). The effect of an increased dosage of chromosome I was preferentially studied in the double aneuploid compared with the single tetrasomy for chromosome VII, since the single tetrasomic for chromosome I tends to revert mitotieaUy when cultured in liquid medium.
Offprint requests to: K. Gull6v
Growth Conditions. Micro-colonies resulting from single cells grown on solid YEPD medium were inspected. A colony with the phenotypie appearence of the aneuploid in question (A. P. James, personal communication) was subcultured in liquid syn-
Yeast strains. The strains used in this study were simple tetrasomy for chromosome I or VII and a double tetrasomy for chromosome I and VII. The strains, kindly provided by Dr. A. P. James, are: S 325-4-5A, 2n + 2VII leul leul/leul leul, ura3/ura3 S 301-8A~ 2n + 21 trpl/trpl S 598-SB,2n+ 2I + 2VII adel adel/adel adel
0172-8083/80/0002/0075/$01.00
76
K. Gullov and J. Friis: Chromosomal Proteins in Yeast II
Table 1. Normalized ratios of labelled chromosomal proteins in nuclear preparations Protein
Combination of genotypes in ratios (3H/14C)
no.
Nuclei 2 3 4 5 6 7 8 10 11 12 13 14 15 16 17 18 19 20 21 22 24 25 26 27 28 29 30 32
2n + 2I + 2VII 2n + 21 + 2VII
2n + 21 + 2VII 2n + 2I
2n + 2VII 2n + 21 + 2VII
1.0 0.95 0.89 0.95 0.87 0.97 0.95 0.79 1.03 0.95 1.03 0.92 1.00 0.89 0.87 1.05 1.03 1.05 0.89 0.92 0.92 1.00 0.92 0.84 0.89 0.84 1.00 1.00
1.0 1.19 0.81 1.05 0.93 0.85 0.79 0.77 0.89 0.99 . 0.95 0.86 1.04 1.09 0.99 0.89 0.91 0.96 0.79 0.77 0.86 0.96 . 1.00
1.0 a 0.94 0.98 0.88 1.13 0.42 0.94 1.25 0.75 0.67 1.04 1.12 . 1.02 1.48 0.96 0.77 0.65 1.02 1.08 1.31 0.71 0.65 0.87 1.29 0.90 . 1.15 -
.
.
1.0 bl 0.75 1.04 1.29 0.57 1.01 1.85 0.70 0.67 -
1.0 b2 0.80 1.01 1.20 0.54 1.03 1.66 0.67 0.67 0.90 -
0.92 0.81 0.57 0.70 -
0.92 0.90 0.95 0.44 1.03 1.39 0.67 0.84 0.76
-
-
.
.
All values represent the average of double estimations (two gels) within one experiment, a) and b) are two separate experiments. In b2) 0.2% SDS was included in the sample prior to the electrophoresis
thetic glucose medium. A serial transfer of the exponentially growing culture was done at most twice before the actual experiment was performed. Colonial phenotyping was done regularly to verify the identity of the cultures.
Separation Methods. Preparation of nuclei, protein extraction and two-dimensional electrophoresis was done essentially as described in the preceding article,
Results
The Nuclear Content of Nonhistone Proteins in Aneuploids. T h e a n e u p l o i d strains were c u l t i v a t e d in s y n t h e t i c glucose m e d i u m s u p p l e m e n t e d w i t h 10 ~ g / m l a d e n i n e sulfate a n d 5 g g / m l uracil. P r o t e i n labelling was carried o u t b y a d d i n g e i t h e r L - [ 4 , 5 - 3 H ] l e u c i n e ( 2 / ~ C / m l ;4/~g/ml)
or
[U-14C]leucine
(0.2 p C / m l ; 4 p g / m l ) . Cells were
l a b e l l e d for at least t w o g e n e r a t i o n s o f g r o w t h a n d h a r v e s t e d at a cell density o f 6 x 106 cells p e r ml. 3H a n d 14C l a b e l l e d s p h e r o p l a s t s o f the d i f f e r e n t a n e u p l o i d s were c o m b i n e d . Nuclei were isolated a n d n u c l e a r proteins were s u b j e c t e d t o t w o - d i m e n s i o n a l poly-acrylamide gel e l e c t r o p h o r e s i s as d e s c r i b e d in the p r e c e d i n g article. T h e 3H/14C ratios o f individual p r o t e i n s , w h i c h varied b e t w e e n 2 a n d 10, h a v e b e e n n o r m a l i z e d t o t h e 3H/14C r a t i o o f t h e n u c l e a r p r e p a r a t i o n in e a c h experim e n t . T h e results are p r e s e n t e d in T a b l e 1. T h e first c o l u m n p r e s e n t s a c o n t r o l e x p e r i m e n t w h e r e c o m b i n e d 3H a n d 14C l a b e l l e d s p h e r o p l a s t s o f the d o u b l e t e t r a s o m i c were m e a s u r e d . As e x p e c t e d the ratios for individual p r o t e i n s are d i s t r i b u t e d w i t h i n a n o r m a l curve o f e r r o r since 67% o f t h e ratios are o b s e r v e d w i t h i n the m e a n -+1 a u n i t . T h e s e c o n d c o l u m n illustrates t h e e f f e c t o f d o u b l i n g the dosage o f c h r o m o s o m e
77
K. Gull~v and J. Friis: Chromosomal Proteins in Yeast II VII in a simple tetrasomy for chromosome I. A moderate, but distinct scattering of ratios is observed since the F value for equality of variances, as compared with the control distribution, exceeds by chance the 5% level. The last columns represent experiments where the doubling of the dosage of chromosome I in a tetrasomy for chromosome VII was analysed. From the scattering of the ratios in the first experiment a), it is evident that the nuclear content of a number of nonhistone proteins is markedly impaired by this doublication. The amount of a number of proteins,no. 6, 10, 11, 18, 19, 24, and 25 is distinctly increased in the nuclear compartment, while the amounts of others are reduced, no. 5, 8, 16, 22 and 27. To establish the marked dosis effect of chromosome I a separate, second experiment was performed. This time the sample was subdivided, and one sample, b2) was supplemented with 0.2% SDS prior to electrophoresis. By this treatment streaking effects in the electrofocusing system are deminished and proteins no. 18 and 19 are resolved as distinct spots. Likewise streaking from proteins no. 10, 11 into the position of no. 25 is avoided (see Fig. 2a of the preceding article). Evidently the marked effect is repeatedly seen. Due to the improved resolution it is noticed that the ratio in no. 19 is markedly reduced, while no. 18 is only slightlyimpaired by the dosis effect. Similarly the ratio of spot no. 25 is little impaired, when streaking from no. 10, 11 is abolished. Compared with the sample figures of the control experiment, the F value for equality of variances of the sample figures of column 2b) reveals a value, which as expected by chance exeeds the 0.2% level.
Table 2. The cellular content of the major nonhistone proteins in two aneuploids with varying dosage of chromosome I Protein no.
Normalized Percentage of cellular protein ratios 3H/14C 2n + 2VII/ 2n + 2VII 2n + 2I + 2VII 2n + 2I + 2VII
Spheroplasts 3 4 5 6 7 8 10 11 18 19 27
1.00 0.96 0.79 0.83 0.60 1.00 1.13 0.63 0.63 0.81 0.67 1.21
100 0.12 0.08
100 0.12 0.09
0.37
0.57
0.15 0.36 a
0.15 0.52a
0.16 b
0.22b
a sum of 10 and 11. b sum of 18and19.
wise, the heterogeneous protein no. 18, 19 which is abundantly associated with nuclear DNA is present in higher amounts in the double tetrasomic strain. On the contrary, the putative RNA polymerase subunit[po123, spot no. 3, is evidently not impaired by the varying dosage of chromosome I.
Discussion
The Cellular Content of Some Major Nonhistone Proteins in Chromosome I Aneuploids The observed effect might be due to a shuttling phenomenon whereby the amount of a number of nonhistone proteins is increased or diminished in the nuclear compartment, or it might be due to an altered rate of synthesis of a number of proteins caused by the dosage effect. Estimation of the cellular content of a number of the major nonhistone proteins in the single and the double tetrasomic seems to favour the last notion. Due to the limited resolving capacity obtained with spheroplast preparations, only the few proteins indicated in Table 2 were quantitatively removed from the gels without contaminants. Except for a single protein, no. 5, the labelling ratios of individual chromosomal proteins from nuclear and cellular extracts show nearly identical patterns. It is noteworthy that the cellular content of iahe tubulin proteins no. 6 and no. 10, 11 in a strain tetrasomy for chromosome I is increased by approximately 50 as compared with a strain disomy for chromosome I. Like-
In these experiments we have demonstrated a marked effect on the nuclear and cellular content of a number of the major nonhistones, when the dosage of chromosome I is doubled in a homothallic aneuploid yeast strain. The coherence of this observation with the aberrant adjustment of the number of rRNA genes in aneuploids of chromosome I is not immediately comprehensible. Both effects may have a common origin. Physiological imbalance in such strains (James et al., 1974) may promote changed levels of a vast number of gene products and promote the growth of recombinants with an increased number of rRNA genes following unequal mitotic crossing-over (Kaback and Halvorson, 1977). Alternatively, a changed nonhistone pattern in the yeast genome might more directly impaire the number of rRNA genes. The aberrant amount of tubulin proteins, which is found in chromosome I aneuploids might be such a hint, since microtubules are involved in the nuclear elongation and possibly thereby in the mitotic chromosomal segregation (Byers and Goetsch, 1973). This would also apply to the proteins no. 18 and 19 since they are almost quantitatively bound to the nuclear DNA.
78 Variations within the nonhistone composition in purified chromatin from different cell types of the same organism have been reported previously (Paulin et al., 1976). In mouse embryonic carcinoma cells the relative amount of contractile proteins and tubulin is reduced by 4 0 - 5 0 % as compared with myoblast and fibroblast cell lines. These authors suggest that the differentiation process leading to the inactivation of a vast number of structural genes is accompanied by an increase of the DNA associated amounts of these proteins. In view of our observations, we would contest this notion, since a similar change is seen in the non-differentiated yeast cell concerning tubulin proteins. In the yeast this effect is attributed to a rather specific aneuploid state of the genome, as it may be in mouse since the embryonic carcinoma cells are normal diploids deviating from the ill defined, aneuploid karyotypes of the differentiated cell lines.
K. Gull4v and J. Friis: Chromosomal Proteins in Yeast II
References Byers, B., Goetsch, L.: Cold Spring Harbor Symp. Quant. Biol. 38, 123-132 (1973) Finkelstein, D. B., Blamire, J., Marmur, J.: Nature New Biol. 240, 279-281 (1972) James, A. P., Inhaber, E. R., Pr~fontaine, G. J.: Genetics 77, 1-9 (1974) Kaback, D. B., Halvorson, H. O.: Proc. Nat. Acad. Sci. USA 74, 1177-1180 (1977) Kaback, D. B., Bhaxgava, M. M., Halvorson, H. O.: J. Mol. Biol. 79, 735-739 (1973) Paulin, D., Nicolas, J. F., Jaquet, M., Jacob, H., Gros, F., Jacob, F.: Exp. Cell Res. 102, 169-178 (1976) Petes, T. D.: Proc. Nat. Acad. Sci. USA 76,410-414 (1979) Petes, T. D., Hereford, L. M., Botstein, D.: Cold Spring Harbor Symp. Quant. Biol. 42, 1201-1207 (1977) Seligy, V. L., James, A. P.: Exp. Cell Res. 105, 63-72 (1977) q)yen, T. B.: FEBS Lett. 30, 53-56 (1973) Communicated by R. J. Schweyen
Acknowledgement. The Carlsberg Foundation has generously supported this work with a grant to one of us (J. F.).
Received November 23, 1979
~ ©
~ by Springer-Verlag 1980
Chromosomal Proteins in Saccharomyces cerevisiae II. C h r o m o s o m e D o s a g e E f f e c t on the Cellular a n d N u c l e a r C o n t e n t o f N o n h i s t o n e P r o t e i n s
Kay Gull6v and J6rgen Friis Department of Molecular Biology, University of Odense, Campusvej 55, DK-5230 Odense M., Denmark
Summary. The effect of varying the chromosomal dosage in aneuploids for chromosome I or VII on the synthesis of individual nonhistone proteins was revealed. The nuclear content of most nonhistone proteins seemed to be little impaired in a strain with tetrasomy for chromosome VII as compared with a strain which is disomic for chromosome VII. On the contrary, tetrasomy for chromosome I as compared with disomy for this chromosome seems to impair both the cellular and the nuclear content of a number of chromosomal proteins, including the tubulin subunits.
Key words: Aneuploid strains - Two-dimensional electrophoresis.
Introduction
These observations led to the suggestion that most or all of the rRNA cistrons in yeast were located on chromosome I. Genetic analysis, involving fusion of haploids with different EcoRI restriction patterns within the rDNA sequence, and subsequent spomlation, have revealed a segregation pattern consistent with the location of the rRNA genes within one linkage group (Petes et al., 1977). Contrary to the previous assumption, elaborate genetic analysis by Petes (1979) indicated that the rRNA genes are linked mitotically to chromosome XII. In view o f these observations we have investigated the gene dosage effect of two chromosomes including no. I on the number and amounts of individual nonhistone proteins in the yeast nucleus to see if the composition of yeast chromatin is specifically impaired.
Materials and Methods
Yeast strains aneuploid for chromosome I exhibit a peculiar adjustment pattern of the number of rRNA cistrons per genome. Saturation hybridization experiments with diploid strains with monosomy for chromo. some I, reveals that the hybridization level with rRNA is reduced approximately 35% (Finkelstein et al., 1972; 0 y e n , 1973; Kaback et al., 1973). Similarly, the hybridization level with rRNA in diploids, which are tetrasomic for chromosome I is increased by 5 0 - 6 0 % (Seligy and James, 1977). A diploid strain which is monosomic for chromosome I and initially deficient for 30% of the rRNA genes, when repeatedly subcultured, increased the number of rRNA genes to a stable level characteristic of a normal diploid (Kaback and Halvorson, 1977).
These strains are essentially homozygous and identical in their genetic background. All strains are derived from a homothallic spore clone, with tetrasomy for chromosome I and VII (Seligy and James, 1977). The effect of an increased dosage of chromosome I was preferentially studied in the double aneuploid compared with the single tetrasomy for chromosome VII, since the single tetrasomic for chromosome I tends to revert mitotieaUy when cultured in liquid medium.
Offprint requests to: K. Gull6v
Growth Conditions. Micro-colonies resulting from single cells grown on solid YEPD medium were inspected. A colony with the phenotypie appearence of the aneuploid in question (A. P. James, personal communication) was subcultured in liquid syn-
Yeast strains. The strains used in this study were simple tetrasomy for chromosome I or VII and a double tetrasomy for chromosome I and VII. The strains, kindly provided by Dr. A. P. James, are: S 325-4-5A, 2n + 2VII leul leul/leul leul, ura3/ura3 S 301-8A~ 2n + 21 trpl/trpl S 598-SB,2n+ 2I + 2VII adel adel/adel adel
0172-8083/80/0002/0075/$01.00
76
K. Gullov and J. Friis: Chromosomal Proteins in Yeast II
Table 1. Normalized ratios of labelled chromosomal proteins in nuclear preparations Protein
Combination of genotypes in ratios (3H/14C)
no.
Nuclei 2 3 4 5 6 7 8 10 11 12 13 14 15 16 17 18 19 20 21 22 24 25 26 27 28 29 30 32
2n + 2I + 2VII 2n + 21 + 2VII
2n + 21 + 2VII 2n + 2I
2n + 2VII 2n + 21 + 2VII
1.0 0.95 0.89 0.95 0.87 0.97 0.95 0.79 1.03 0.95 1.03 0.92 1.00 0.89 0.87 1.05 1.03 1.05 0.89 0.92 0.92 1.00 0.92 0.84 0.89 0.84 1.00 1.00
1.0 1.19 0.81 1.05 0.93 0.85 0.79 0.77 0.89 0.99 . 0.95 0.86 1.04 1.09 0.99 0.89 0.91 0.96 0.79 0.77 0.86 0.96 . 1.00
1.0 a 0.94 0.98 0.88 1.13 0.42 0.94 1.25 0.75 0.67 1.04 1.12 . 1.02 1.48 0.96 0.77 0.65 1.02 1.08 1.31 0.71 0.65 0.87 1.29 0.90 . 1.15 -
.
.
1.0 bl 0.75 1.04 1.29 0.57 1.01 1.85 0.70 0.67 -
1.0 b2 0.80 1.01 1.20 0.54 1.03 1.66 0.67 0.67 0.90 -
0.92 0.81 0.57 0.70 -
0.92 0.90 0.95 0.44 1.03 1.39 0.67 0.84 0.76
-
-
.
.
All values represent the average of double estimations (two gels) within one experiment, a) and b) are two separate experiments. In b2) 0.2% SDS was included in the sample prior to the electrophoresis
thetic glucose medium. A serial transfer of the exponentially growing culture was done at most twice before the actual experiment was performed. Colonial phenotyping was done regularly to verify the identity of the cultures.
Separation Methods. Preparation of nuclei, protein extraction and two-dimensional electrophoresis was done essentially as described in the preceding article,
Results
The Nuclear Content of Nonhistone Proteins in Aneuploids. T h e a n e u p l o i d strains were c u l t i v a t e d in s y n t h e t i c glucose m e d i u m s u p p l e m e n t e d w i t h 10 ~ g / m l a d e n i n e sulfate a n d 5 g g / m l uracil. P r o t e i n labelling was carried o u t b y a d d i n g e i t h e r L - [ 4 , 5 - 3 H ] l e u c i n e ( 2 / ~ C / m l ;4/~g/ml)
or
[U-14C]leucine
(0.2 p C / m l ; 4 p g / m l ) . Cells were
l a b e l l e d for at least t w o g e n e r a t i o n s o f g r o w t h a n d h a r v e s t e d at a cell density o f 6 x 106 cells p e r ml. 3H a n d 14C l a b e l l e d s p h e r o p l a s t s o f the d i f f e r e n t a n e u p l o i d s were c o m b i n e d . Nuclei were isolated a n d n u c l e a r proteins were s u b j e c t e d t o t w o - d i m e n s i o n a l poly-acrylamide gel e l e c t r o p h o r e s i s as d e s c r i b e d in the p r e c e d i n g article. T h e 3H/14C ratios o f individual p r o t e i n s , w h i c h varied b e t w e e n 2 a n d 10, h a v e b e e n n o r m a l i z e d t o t h e 3H/14C r a t i o o f t h e n u c l e a r p r e p a r a t i o n in e a c h experim e n t . T h e results are p r e s e n t e d in T a b l e 1. T h e first c o l u m n p r e s e n t s a c o n t r o l e x p e r i m e n t w h e r e c o m b i n e d 3H a n d 14C l a b e l l e d s p h e r o p l a s t s o f the d o u b l e t e t r a s o m i c were m e a s u r e d . As e x p e c t e d the ratios for individual p r o t e i n s are d i s t r i b u t e d w i t h i n a n o r m a l curve o f e r r o r since 67% o f t h e ratios are o b s e r v e d w i t h i n the m e a n -+1 a u n i t . T h e s e c o n d c o l u m n illustrates t h e e f f e c t o f d o u b l i n g the dosage o f c h r o m o s o m e
77
K. Gull~v and J. Friis: Chromosomal Proteins in Yeast II VII in a simple tetrasomy for chromosome I. A moderate, but distinct scattering of ratios is observed since the F value for equality of variances, as compared with the control distribution, exceeds by chance the 5% level. The last columns represent experiments where the doubling of the dosage of chromosome I in a tetrasomy for chromosome VII was analysed. From the scattering of the ratios in the first experiment a), it is evident that the nuclear content of a number of nonhistone proteins is markedly impaired by this doublication. The amount of a number of proteins,no. 6, 10, 11, 18, 19, 24, and 25 is distinctly increased in the nuclear compartment, while the amounts of others are reduced, no. 5, 8, 16, 22 and 27. To establish the marked dosis effect of chromosome I a separate, second experiment was performed. This time the sample was subdivided, and one sample, b2) was supplemented with 0.2% SDS prior to electrophoresis. By this treatment streaking effects in the electrofocusing system are deminished and proteins no. 18 and 19 are resolved as distinct spots. Likewise streaking from proteins no. 10, 11 into the position of no. 25 is avoided (see Fig. 2a of the preceding article). Evidently the marked effect is repeatedly seen. Due to the improved resolution it is noticed that the ratio in no. 19 is markedly reduced, while no. 18 is only slightlyimpaired by the dosis effect. Similarly the ratio of spot no. 25 is little impaired, when streaking from no. 10, 11 is abolished. Compared with the sample figures of the control experiment, the F value for equality of variances of the sample figures of column 2b) reveals a value, which as expected by chance exeeds the 0.2% level.
Table 2. The cellular content of the major nonhistone proteins in two aneuploids with varying dosage of chromosome I Protein no.
Normalized Percentage of cellular protein ratios 3H/14C 2n + 2VII/ 2n + 2VII 2n + 2I + 2VII 2n + 2I + 2VII
Spheroplasts 3 4 5 6 7 8 10 11 18 19 27
1.00 0.96 0.79 0.83 0.60 1.00 1.13 0.63 0.63 0.81 0.67 1.21
100 0.12 0.08
100 0.12 0.09
0.37
0.57
0.15 0.36 a
0.15 0.52a
0.16 b
0.22b
a sum of 10 and 11. b sum of 18and19.
wise, the heterogeneous protein no. 18, 19 which is abundantly associated with nuclear DNA is present in higher amounts in the double tetrasomic strain. On the contrary, the putative RNA polymerase subunit[po123, spot no. 3, is evidently not impaired by the varying dosage of chromosome I.
Discussion
The Cellular Content of Some Major Nonhistone Proteins in Chromosome I Aneuploids The observed effect might be due to a shuttling phenomenon whereby the amount of a number of nonhistone proteins is increased or diminished in the nuclear compartment, or it might be due to an altered rate of synthesis of a number of proteins caused by the dosage effect. Estimation of the cellular content of a number of the major nonhistone proteins in the single and the double tetrasomic seems to favour the last notion. Due to the limited resolving capacity obtained with spheroplast preparations, only the few proteins indicated in Table 2 were quantitatively removed from the gels without contaminants. Except for a single protein, no. 5, the labelling ratios of individual chromosomal proteins from nuclear and cellular extracts show nearly identical patterns. It is noteworthy that the cellular content of iahe tubulin proteins no. 6 and no. 10, 11 in a strain tetrasomy for chromosome I is increased by approximately 50 as compared with a strain disomy for chromosome I. Like-
In these experiments we have demonstrated a marked effect on the nuclear and cellular content of a number of the major nonhistones, when the dosage of chromosome I is doubled in a homothallic aneuploid yeast strain. The coherence of this observation with the aberrant adjustment of the number of rRNA genes in aneuploids of chromosome I is not immediately comprehensible. Both effects may have a common origin. Physiological imbalance in such strains (James et al., 1974) may promote changed levels of a vast number of gene products and promote the growth of recombinants with an increased number of rRNA genes following unequal mitotic crossing-over (Kaback and Halvorson, 1977). Alternatively, a changed nonhistone pattern in the yeast genome might more directly impaire the number of rRNA genes. The aberrant amount of tubulin proteins, which is found in chromosome I aneuploids might be such a hint, since microtubules are involved in the nuclear elongation and possibly thereby in the mitotic chromosomal segregation (Byers and Goetsch, 1973). This would also apply to the proteins no. 18 and 19 since they are almost quantitatively bound to the nuclear DNA.
78 Variations within the nonhistone composition in purified chromatin from different cell types of the same organism have been reported previously (Paulin et al., 1976). In mouse embryonic carcinoma cells the relative amount of contractile proteins and tubulin is reduced by 4 0 - 5 0 % as compared with myoblast and fibroblast cell lines. These authors suggest that the differentiation process leading to the inactivation of a vast number of structural genes is accompanied by an increase of the DNA associated amounts of these proteins. In view of our observations, we would contest this notion, since a similar change is seen in the non-differentiated yeast cell concerning tubulin proteins. In the yeast this effect is attributed to a rather specific aneuploid state of the genome, as it may be in mouse since the embryonic carcinoma cells are normal diploids deviating from the ill defined, aneuploid karyotypes of the differentiated cell lines.
K. Gull4v and J. Friis: Chromosomal Proteins in Yeast II
References Byers, B., Goetsch, L.: Cold Spring Harbor Symp. Quant. Biol. 38, 123-132 (1973) Finkelstein, D. B., Blamire, J., Marmur, J.: Nature New Biol. 240, 279-281 (1972) James, A. P., Inhaber, E. R., Pr~fontaine, G. J.: Genetics 77, 1-9 (1974) Kaback, D. B., Halvorson, H. O.: Proc. Nat. Acad. Sci. USA 74, 1177-1180 (1977) Kaback, D. B., Bhaxgava, M. M., Halvorson, H. O.: J. Mol. Biol. 79, 735-739 (1973) Paulin, D., Nicolas, J. F., Jaquet, M., Jacob, H., Gros, F., Jacob, F.: Exp. Cell Res. 102, 169-178 (1976) Petes, T. D.: Proc. Nat. Acad. Sci. USA 76,410-414 (1979) Petes, T. D., Hereford, L. M., Botstein, D.: Cold Spring Harbor Symp. Quant. Biol. 42, 1201-1207 (1977) Seligy, V. L., James, A. P.: Exp. Cell Res. 105, 63-72 (1977) q)yen, T. B.: FEBS Lett. 30, 53-56 (1973) Communicated by R. J. Schweyen
Acknowledgement. The Carlsberg Foundation has generously supported this work with a grant to one of us (J. F.).
Received November 23, 1979
