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17. Single-letter abbreviations for the amino acid residues
are as follows: A, Ala; C, Cys; D, Asp; E, Glu; F, Phe;
G, Gly; H, His; I, Ile; K, Lys; L, Leu; M, Met; N, Asn; P,
Pro; Q, Gln; R, Arg; S, Ser; T, Thr; V, Val; W, Trp;
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19. We thank S. J. Han for Wee1B plasmids, K. T. Jones for
cyclin B plasmids, and T. Lorca for the CaMKII plasmid.
This work was supported by NIH grants GM080527-05
and HD052909. J.O. designed, performed, and analyzed
most of the experiments in this study. A.S. performed
immunostaining. M.C. conceived the project and supervised
the study. J.O. and M.C. wrote the manuscript.
Supporting Online Material
Materials and Methods
Figs. S1 to S6
18 October 2010; accepted 17 March 2011
Published online 31 March 2011;
A Midzone-Based Ruler Adjusts
Chromosome Compaction to
Anaphase Spindle Length
Gabriel Neurohr,1,2 Andreas Naegeli,2 Iris Titos,1 Dominik Theler,2 Basil Greber,2
Javier Díez,1 Toni Gabaldón,1 Manuel Mendoza,1,2† Yves Barral2†
Partitioning of chromatids during mitosis requires that chromosome compaction and spindle
length scale appropriately with each other. However, it is not clear whether chromosome
condensation and spindle elongation are linked. Here, we find that yeast cells could cope
with a 45% increase in the length of their longest chromosome arm by increasing its condensation.
The spindle midzone, aurora/Ipl1 activity, and Ser10 of histone H3 mediated this response.
Thus, the anaphase spindle may function as a ruler to adapt the condensation of chromatids,
promoting their segregation regardless of chromosome or spindle length.
During animal cell division, chromosome partitioning requires mitotic chromo- somes to be compact enough to allow
their segregation; conversely, the spindle must
elongate enough to segregate even the longest
chromosome (1, 2). To address how cells cope
with a highly oversized chromosome, we generated a very long chromosome arm (where
“chromosome length” refers to nucleotide number). The two longest chromosomes (IV and XII)
of budding yeast were fused by homologous
recombination in vivo to form the long compound chromosome LC(XII:IV) (Fig. 1A) (3).
To prevent dicentric chromosome formation, the
centromere CEN4 was inactivated in galactose-containing medium by the GAL1-10 promoter
(4). GAL1:CEN4 cells grew poorly in galactose,
due to chromosome IV instability (Fig. 1B). In
contrast, LC(XII:IV)GAL:CEN4 cells grew well
in galactose, consistent with segregation of chromosome IV with CEN12, whereas they grew
poorly in glucose, owing to dicentric chromo-
1Centre for Genomic Regulation (CRG), and Universitat Pompeu
Fabra (UPF), Barcelona, Spain. 2Institute of Biochemistry,
Biology Department, Eidgenössische Technische Hochschule
(ETH) Zurich, 8093 Zurich, Switzerland.
*These authors contributed equally to this work.
†To whom correspondence should be addressed. E-mail:
firstname.lastname@example.org (M.M.); email@example.com
some formation (Fig. 1B). We next generated
the true monocentric compound chromosomes
LC(XII:IV)cen4Δ and LC(XII:IV)cen12Δ by deleting CEN4 and CEN12, respectively (fig. S1).
Whole genome sequencing showed that gene
order and intergenic distances were conserved
between wild-type and LC(XII:IV) strains and
identified no genomic rearrangements other than
the fusion of chromosomes IV and XII (fig. S2).
Quantitative polymerase chain reaction (qPCR)
analysis indicated that the number of ribosomal DNA (rDNA) repeats was reduced by 6
to 25% in LC(XII:IV)cen4Δ strains relative to
wild-type chromosome XII (87 to 110 repeats
versus 110 to 120) (fig. S3). This established
that even after rDNA array shortening the
long arm of LC(XII:IV) was 45% longer than
the longest wild-type arm (3.2 versus 2.2 Mb).
Thus, yeast cells tolerate remarkably well a large
increase in the length of their longest chromosome arm, although they have probably not
experienced it naturally over the past 100 million years (3).
We next examined how cells segregate
LC(XII:IV ) chromosomes. Anaphase spindle elon-
gation, visualized by fusing the spindle pole body
(SPB) component Spc42 to green fluorescent
protein (Spc42-GFP), progressed with identical
kinetics in wild-type and LC(XII:IV)cen4Δ cells,
to reach identical lengths (Fig. 1, C to E). Thus,
to segregate this long chromosome, cells did not
need to elongate the spindle more or prolong