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Advances in Brief |
in Somatic and Meiotic Cells1
Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 [F. B. J., D. B. L., R. A. M., L. G.]; Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts 02115 [F. B. J.]; Division of Hematology-Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114 [R. A. M.]; Laboratory of Molecular Genetics, New York Blood Center, New York, New York 10021 [N. F. N.]; Whitehead Institute, Cambridge, Massachusetts 02142 [M-A. M., R. J.]; Beth Israel/Deaconess Medical Center, Boston, Massachusetts 02215 [W. D., Y. Y.]; and Laboratory of Cancer Susceptibility, Memorial Sloan-Kettering Cancer Research Center, New York, New York 10021 [N. A. E.]
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ABSTRACT |
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 Top ABSTRACT IntroductionMaterials and MethodsResultsDiscussionNote Added in ProofREFERENCES |
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. These proteins colocalize in
promyelocytic leukemia protein nuclear bodies, and this localization is
disrupted in BS cells. Thus, mechanisms by which RecQ helicases and
topoisomerase III proteins cooperate to maintain genomic stability in
model organisms likely apply to humans. |
Introduction |
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TopABSTRACTIntroductionMaterials and MethodsResultsDiscussionNote Added in ProofREFERENCES |
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proteins in human cells. |
Materials and Methods |
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TopABSTRACTIntroductionMaterials and MethodsResultsDiscussionNote Added in ProofREFERENCES |
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COOH-terminal fragment expression plasmid was generated
by inserting the 1.2-kb TOP3 PpuMI-EcoRI cDNA
fragment (gift of J. Wang, Harvard University) into the
NheI and EcoRI sites of pET28a(+) (Novagen).
Chicken anti-BLM antibodies were derived against nucleotides 3149–4328
of the human coding sequence cloned into pET28a via PCR.
Cells.
Lymphoblastoid cells AG07877 (WT) and AG04103 (WS, homozygous for
R369X), both obtained from the Coriell Repository, and HG1525 (BS,
homozygous for S595X, gift of J. German, Cornell Medical School) were
grown in RPMI 1640, 4 mM glutamine, 1x Pen-Strep, and 15%
heat-inactivated fetal bovine serum. WI38 (WT) and AG2940 (BS, gift of
J. German, Cornell Medical School) fibroblasts were grown in
DMEM/1 x Pen-Strep/20% fetal bovine serum.
Antibodies.
Topo III antibodies were raised in chickens and rabbits (Covance)
using the COOH-terminal 211 amino acids of Topo III fused to a 6XHIS
tag that had been expressed in E. coli BL21(DE3) and
purified using Ni-NTA resin (Qiagen). Affinity-purified rabbit
antibodies directed against the NH2-terminal
portion of BLM were generated as described (8)
. A BLM
fragment encoding amino acids 3149–4328 was used to immunize chickens
(Covance). Topo III and chicken BLM antibodies were affinity
purified using the immunizing antigen coupled to Aminolink resin
(Pierce). RECQL antiserum (1145) was a kind gift of Debbie Stumpo and
Perry Blackshear (7)
. Anti-PML (PG-M3) was obtained from
Santa Cruz Biotechnology. Anti-SCP3 antibody was the kind gift of
Christa Heyting (9)
.
Immunofluorescence.
Early passage WI-38 or AG2940 (BS) human diploid fibroblasts were grown
on multiwell slides. Slides were prepared using preextraction and
paraformaldehyde fixation as described (10)
. Secondary
antibodies were purchased from Vector Laboratories. Chicken antibodies
were detected with biotinylated antichicken antibodies and then
developed with Cy3-avidin (Amersham or Sigma). Meiotic spreads were
prepared by standard techniques (11)
from testes removed
for prostate cancer or chronic pain, and indirect immunofluorescence
was performed as for fibroblasts. To visualize the synaptonemal
complex, anti-SCP3 was included in the tertiary incubation, and the
slides were washed as above and then incubated in blocking buffer plus
1:100 AMCA-conjugated antirabbit (Vector) for an additional 30
min. Control experiments demonstrated that even when another rabbit
antibody had been used during the first incubation, there was no
detectable binding of AMCA antirabbit to the initial primary
antibody. Stained slides were mounted in Vectashield (Vector
Laboratories). Slides were imaged at x100 on a CCD camera, and the
images were pseudocolored and merged in Adobe Photoshop.
Extracts and Immunoprecipitations.
Whole-cell extracts were prepared from log-phase lymphoblastoid cells,
essentially as described (12)
, except that the final
dialysis buffer contained 150 mM KOAc. Extract preparation
included centrifugation at 150,000 x g to
remove insoluble chromatin, followed by a 0.33 g/ml
(NH4)SO4 precipitation
step. For IPs, 100 µg of extract protein in a final volume of 25 µl
IP buffer [20 mM TrisOAc (pH 7.9), 150
mM KOAc, 1 mM EDTA, 5%
glycerol, 0.1 mM DTT, 0.05% NP40, 0.2 mg/ml BSA,
1 mM phenylmethylsulfonyl fluoride, and 5 µg/ml
each aprotinin, leupeptin, and pepstatin A] were mixed with 2.5 µl
of beads [protein A-Sepharose (Sigma) for rabbit antibodies or
anti-IgY agarose (Promega) for chicken antibodies] for 15 min at
4°C, followed by a 16,000 x g spin at
4°C for 5 min to preclear the extract. The supernatant was mixed with
5 µl of fresh beads and antibody (equal concentrations of control or
experimental antibody) and mixed at 4°C for 1 h. The supernatant
was removed, and beads were washed once with 250 µl of IP buffer and
then three times with 250 µl of wash buffer [20
mM TrisOAc (pH 7.9), 150 mM
KOAc, 0.1 mM EDTA, 6 mM
Mg(OAc)2, 0.1 mM DTT,
0.05% NP40, and 0.2 mg/ml BSA]. Proteins retained by the beads were
separated by SDS-PAGE, followed by transfer to nitrocellulose and
detection by standard immunoblotting using ECL.
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Results |
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TopABSTRACTIntroductionMaterials and MethodsResultsDiscussionNote Added in ProofREFERENCES |
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and Topo IIIß. Topo III is the most similar to
yeast Top3p, sharing 44% sequence identity (13)
.
Antibodies were raised in chickens and rabbits to the COOH-terminal 211
amino acids of the human Topo III protein. Because these residues
are contained within a COOH-terminal extension that is not
substantially conserved in Topo IIIß, this strategy ensured that
these antibodies would not cross-react with Topo IIIß.
Affinity-purified antibodies recognized a protein of
Mr 110,000 on immunoblots of
human cell extracts (Fig. 1A)
, consistent with the predicted size of Topo III, as
well a Mr 70,000 species judged to be
a degradation product because it increases in relative abundance with
freeze-thaws of the extract (not shown). Immunoprecipitation was used
to test for association between BLM and Topo III, using
lymphoblastoid cell extracts from which bulk chromatin had been removed
(see "Materials and Methods"). BLM coprecipitated with Topo III
using the chicken anti-Topo III antibody 1003 (Fig. 1B)
.
A second human RecQ-family helicase, RECQL, also coprecipitated with
Topo III (Fig. 1B)
. Ethidium bromide can disrupt
protein-DNA interactions and so has been used to distinguish
protein-protein interactions from those mediated by binding of factors
to DNA (14)
. Coprecipitation of BLM or RECQL with Topo
III persisted in the presence of 100 µg/ml ethidium bromide (Fig. 1B
, top) and also persisted after treatment of the
precipitates with DNase I and RNase A at 37°C (Fig. 1B
,
bottom). Thus, the associations did not depend on binding of the
proteins to residual nucleic acids in the extracts although:
(a) the reduction in the BLM-Topo III association by
ethidium bromide might indicate some stabilization of the complex by
DNA; and (b) other factors could still be important for the
observed associations. Similar results for BLM and RECQL were obtained
with extracts of HeLa cells and using the anti-Topo III antibodies
1002 or 1151 (data not shown). Topo II, nuclear factor-
B,
proliferating cell nuclear antigen, or nucleophosmin did not
coprecipitate with Topo III, indicating specificity of the observed
interactions (data not shown).
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in extracts of WT or WS cells but failed to coprecipitate
Topo III from extracts from BS cells, thus demonstrating the
specificity of the anti-BLM precipitations (Fig. 1C)
.
Anti-RECQL antibodies (7)
also coprecipitated Topo III,
and the interaction was independent of the presence of BLM or WRN (Fig. 1D)
. BLM and RECQL do not coimmunoprecipitate (data not
shown), suggesting that Topo III exists in distinct complexes with
BLM or RECQL. We have not observed an interaction between Topo III
and WRN, despite efficient precipitation of WRN with antibodies
directed against either the NH2 or COOH terminus
of WRN (data not shown).
To identify cellular loci where Topo III, BLM, and RECQL
associate, the localization of these proteins in cultured primary human
fibroblasts was examined by indirect immunofluorescence. Topo III
and BLM each were found diffusely throughout the nucleoplasm, in bright
nuclear foci (Fig. 2A
, filled arrowheads), and occasionally in the nucleolus
(Fig. 2A
, open arrowhead). No BLM staining was observed in
BS fibroblasts (not shown). Costaining with rabbit anti-BLM and chicken
anti-Topo III revealed that most of the BLM foci contain Topo III
(Fig. 2A)
. Rabbit anti-RECQL antibodies revealed diffuse
nuclear staining, as observed previously (7)
, as well as
discrete foci similar to those observed with BLM antisera. Costaining
for RECQL and Topo III also revealed substantial colocalization of
the two proteins in a subset of the Topo III foci (Fig. 2B)
. Greater than 90% of cells showed colocalization of
Topo III with the foci containing BLM or RECQL. Colocalization was
apparent in the G1, S, and
G2 phases of the cell cycle, as determined using
primary fibroblasts synchronized by double thymidine block, but was not
observed in cells arrested by serum starvation, indicating that
association depends on the cells being in cycle (data not shown).
Costaining with chicken anti-BLM and rabbit anti-RECQL revealed that
most of the foci contain both helicases (Fig. 2C)
. The
number and appearance of these foci suggested that they might be PML
NBs, structures of uncertain function containing over 20 identified
proteins (15)
, and we confirmed this by costaining with
BLM, RECQL, or Topo III antiserum together with PML antiserum (Fig. 2, D and E)
. Despite their localization at NBs,
we do not observe coprecipitation of BLM or RECQL with the PML protein
that is in the cell extracts (data not shown), arguing that the protein
associations that we do observe are specific and not simply artifacts
of nuclear proximity. Topo III was examined in fibroblast lines from
two different BS individuals and was found diffusely throughout the
nucleus and no longer colocalized with PML, indicating that BLM is
required for proper localization of Topo III to NBs (Fig. 2F
and data not shown).
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may play roles in
meiosis. In yeast, top3 and sgs1 mutants each
display sporulation defects that are suppressed by mutations that
abolish meiotic recombination, indicating that Top3p and Sgs1p are
likely important for the resolution of meiotic recombination
intermediates (16
, 17) . In mice, BLM and Topo III mRNAs
are highly expressed in testis (18)
, and the BLM protein
has been shown recently to localize at synaptonemal complexes
(19)
. Finally, mates with BS are infertile due to failed
spermatogenesis (1)
. We examined the possibility that BLM
and Topo III might be present together on meiotic chromosomes.
Meiotic spreads of human testes were immunostained using chicken
anti-Topo III antiserum and a polyclonal rabbit antiserum against
SCP3 (9)
. This protein marks the axial elements that form
between sister chromatids prior to synapsis of homologous chromosomes
and later marks the lateral elements of the synaptonemal complex after
synapsis. In meiotic spreads in the leptonemal stage of prophase I,
prior to the onset of synapsis, Topo III is distributed throughout
the nucleus, with no specific staining observed on the axial elements
(data not shown). However, during early zygonema, as the autosomes
initiate pairing, strong focal Topo III staining is visible on the
axial elements (Fig. 3, A and B)
. This axial Topo III staining
continues to be visible throughout zygonema as pairing proceeds (Fig. 3B)
. The foci are particularly numerous and intense on
chromosomes that appear to be in the process of pairing and are found
on both asynapsed axial and synapsed lateral elements. Later, in
pachynema, a time at which the X and Y chromosomes partially synapse,
Topo III staining was found diffusely throughout the nucleus with no
axial staining on the X and Y chromosomes (data not shown). BLM has
been reported recently to localize to discrete foci along meiotic
chromosomes in the mouse (19)
, and we asked whether BLM
and Topo III colocalize on human meiotic chromosomes as they do in
somatic cells. Meiotic spreads were costained with affinity-purified
chicken anti-Topo III and rabbit anti-BLM antisera, and substantial
coincidence of the BLM and Topo III was observed (Fig. 3C)
. Meiotic spreads were also stained for an unrelated
recombination protein, Rad51, which localizes at meiotic chromosome
foci (20)
; no overlap was observed between Rad51 and
either BLM or Topo III staining, reinforcing the specificity of the
BLM-Topo III colocalization (data not shown). In some cases, meiotic
spreads were stained for BLM and Topo III and then stained for axial
elements using rabbit anti-SCP3 (Fig. 3D)
. Colocalization of
BLM and Topo III was observed on lateral and some axial elements.
Similar results were obtained using the rabbit anti-Topo III
antiserum and a chicken antiserum directed against the COOH terminus of
the BLM protein (data not shown). Focal RECQL staining was not observed
on meiotic spreads (data not shown).
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Discussion |
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TopABSTRACTIntroductionMaterials and MethodsResultsDiscussionNote Added in ProofREFERENCES |
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associates with the BLM and RECQL
DNA helicases, and that one site of association of these proteins is
the PML NB. The subcellular distributions of the proteins are not fully
coincident by immunolocalization, indicating that they may have
functions apart from one another as well as together. Partial overlap
between BLM and Topo III is also observed in meiotic spreads of
human testes, suggesting cooperation between these proteins in the germ
line as well as in somatic cells. This is the first demonstration of an
interacting partner for the BLM protein.
The E. coli proteins RecQ and Topo III together can catalyze
the passage of double-stranded DNA, most likely through two sequential
single-strand transfers (5)
. Our finding that BLM
associates with Topo III suggests that these proteins cooperate in a
similar fashion in humans. In yeast, Top3p and Sgs1p both function to
antagonize recombination (4
, 17)
, and BS cells also show
elevated recombination (21)
. BLM and Topo III thus
likely influence the frequency or fidelity of recombination events. One
possibility is that they perform this function by disrupting nascent
joint molecules; BLM helicase activity would disrupt base pairing
between the invading strand and target, whereas Topo III would
disentangle the joint molecule by allowing the invading strand to pass
through the target. Such a role for a topoisomerase in recombination
was proposed by Wang et al. (22)
and is
mechanistically similar to the catenation reaction catalyzed by
E. coli RecQ and Topo III in vitro
(5)
. Alternatively, the proteins might promote or reverse
the process of branch migration of Holliday junctions, either directly
or by removing DNA structures that impede branch migration. For
example, the BLM helicase could catalyze helix unwinding, and Topo
III could relieve negative supercoils which, if the DNA duplexes
were not free to rotate, would accumulate behind the migrating Holliday
junction. Failure to resolve recombination intermediates could account
for the high frequency of chromosomal nondisjunction observed in
sgs1 mutants cells and the high incidence of chromosomal
breaks and translocations in BS cells. The partial colocalization of
BLM and Topo III on meiotic chromosomes of human testes also
supports a role for these proteins in meiotic recombination. Our
results are consistent with the previous localization of BLM to meiotic
chromosomes and with the proposed role for yeast Top3p and Sgs1p in
resolving meiotic recombination intermediates (16
, 19)
.
Failure to resolve recombinational intermediates could account for the
meiotic defects in sgs1 and top3 mutants and the
hypogonadism of BS patients.
BLM and Topo III colocalize in PML NBs, although association might
also occur at other sites not revealed by immunofluorescence. Very
recently, others have shown independently that BLM localizes to NBs
(23
, 24)
. Remarkably, immortalized human cells that lack
telomerase and are believed to maintain their telomeres via
recombinational mechanisms show telomeric localization of PML bodies
containing the recombination proteins Rad51 and Rad52
(25)
. Taken together with our findings, these observations
implicate NBs in recombination. Loss of Topo III from NBs in BS
cells suggests that the failure to localize Topo III to NBs might
contribute to the genome instability in BS. Thus, in addition to
hypothesized roles in transcription, replication, and apoptosis
(15)
, NBs might function in recombination.
In summary, here we have shown that BLM associates with the Topo III
protein in human cells. Additional studies are necessary to elucidate
the precise roles that this complex may play in recombination and in
the suppression of cancer.
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Note Added in Proof |
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TopABSTRACTIntroductionMaterials and MethodsResultsDiscussionNote Added in ProofREFERENCES |
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are in press: Wu, L., Davies, S. L., North, P. S.,
Goulaouic, H., Riow, J-F., Turley, H., Gatter, K. C., and Hickson, I.
D. The Bloom’s Syndrome gene product interacts with topoisomerase III.
J. Biol. Chem. in press, 2000.
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ACKNOWLEDGMENTS |
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cDNA, and the members of the Guarente and Jaenisch laboratories for
discussions. |
FOOTNOTES |
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1 This work was supported by National Institute on
Aging Grants R01 AG11119 (to L. G.) and K08 AG00775 and a
Howard Hughes Medical Institute postdoctoral fellowship (to
F. B. J.). D. B. L. is supported by a Medical Scientist Training
Program Grant to Harvard Medical School. 
2 These authors contributed equally to this
work.
3 To whom requests for reprints should be
addressed, at Department of Biology, 68-280, Massachusetts Institute of
Technology, 77 Massachusetts Avenue, Cambridge, MA 02139. Phone:
(617) 253-6965; Fax: (617) 253-8699; E-mail: leng{at}mit.edu
4 The abbreviations used are: BS, Bloom syndrome;
WS, Werner syndrome; WT, wild type; Topo, topoisomerase; PML,
promyelocytic leukemia protein; NB, nuclear body; IP,
immunoprecipitation.
Received 11/22/99. Accepted 1/19/00.
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REFERENCES |
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TopABSTRACTIntroductionMaterials and MethodsResultsDiscussionNote Added in ProofREFERENCES |
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, its fusion partners, and their roles in the pathogenesis of acute promyelocytic leukemia. Blood, 93: 3167-3215, 1999.This article has been cited by other articles:
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|
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J. A. Cobb and L. Bjergbaek RecQ helicases: lessons from model organisms Nucleic Acids Res., September 10, 2006; 34(15): 4106 - 4114. [Abstract] [Full Text] [PDF]
|
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M. Seki, T. Nakagawa, T. Seki, G. Kato, S. Tada, Y. Takahashi, A. Yoshimura, T. Kobayashi, A. Aoki, M. Otsuki, et al. Bloom Helicase and DNA Topoisomerase III{alpha} Are Involved in the Dissolution of Sister Chromatids. Mol. Cell. Biol., August 1, 2006; 26(16): 6299 - 6307. [Abstract] [Full Text] [PDF]
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|
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|
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R.-b. Guo, P. Rigolet, L. Zargarian, S. Fermandjian, and X. G. Xi Structural and functional characterizations reveal the importance of a zinc binding domain in Bloom's syndrome helicase Nucleic Acids Res., June 1, 2005; 33(10): 3109 - 3124. [Abstract] [Full Text] [PDF]
|
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|
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|
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 W. Li, S.-M. Kim, J. Lee, and W. G. Dunphy Absence of BLM leads to accumulation of chromosomal DNA breaks during both unperturbed and disrupted S phases J. Cell Biol., June 21, 2004; 165(6): 801 - 812. [Abstract] [Full Text] [PDF]
|
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|
|
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C. Wicky, A. Alpi, M. Passannante, A. Rose, A. Gartner, and F. Muller Multiple Genetic Pathways Involving the Caenorhabditis elegans Bloom's Syndrome Genes him-6, rad-51, and top-3 Are Needed To Maintain Genome Stability in the Germ Line Mol. Cell. Biol., June 1, 2004; 24(11): 5016 - 5027. [Abstract] [Full Text] [PDF]
|
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S. Sharma, J. A. Sommers, L. Wu, V. A. Bohr, I. D. Hickson, and R. M. Brosh Jr. Stimulation of Flap Endonuclease-1 by the Bloom's Syndrome Protein J. Biol. Chem., March 12, 2004; 279(11): 9847 - 9856. [Abstract] [Full Text] [PDF]
|
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H. Gao, X.-B. Chen, and C. H. McGowan Mus81 Endonuclease Localizes to Nucleoli and to Regions of DNA Damage in Human S-phase Cells Mol. Biol. Cell, December 1, 2003; 14(12): 4826 - 4834. [Abstract] [Full Text] [PDF]
|
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B. Cheng, C.-X. Zhu, C. Ji, A. Ahumada, and Y.-C. Tse-Dinh Direct Interaction between Escherichia coli RNA Polymerase and the Zinc Ribbon Domains of DNA Topoisomerase I J. Biol. Chem., August 15, 2003; 278(33): 30705 - 30710. [Abstract] [Full Text] [PDF]
|
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|
 W. M. Fricke and S. J. Brill Slx1--Slx4 is a second structure-specific endonuclease functionally redundant with Sgs1--Top3 Genes & Dev., July 15, 2003; 17(14): 1768 - 1778. [Abstract] [Full Text] [PDF]
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A. R. Meetei, S. Sechi, M. Wallisch, D. Yang, M. K. Young, H. Joenje, M. E. Hoatlin, and W. Wang A Multiprotein Nuclear Complex Connects Fanconi Anemia and Bloom Syndrome Mol. Cell. Biol., May 15, 2003; 23(10): 3417 - 3426. [Abstract] [Full Text] [PDF]
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S. A. Bastin-Shanower, W. M. Fricke, J. R. Mullen, and S. J. Brill The Mechanism of Mus81-Mms4 Cleavage Site Selection Distinguishes It from the Homologous Endonuclease Rad1-Rad10 Mol. Cell. Biol., May 15, 2003; 23(10): 3487 - 3496. [Abstract] [Full Text] [PDF]
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W. Wang, M. Seki, Y. Narita, T. Nakagawa, A. Yoshimura, M. Otsuki, Y.-i. Kawabe, S. Tada, H. Yagi, Y. Ishii, et al. Functional Relation among RecQ Family Helicases RecQL1, RecQL5, and BLM in Cell Growth and Sister Chromatid Exchange Formation Mol. Cell. Biol., May 15, 2003; 23(10): 3527 - 3535. [Abstract] [Full Text] [PDF]
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L. V. Laursen, E. Ampatzidou, A. H. Andersen, and J. M. Murray Role for the Fission Yeast RecQ Helicase in DNA Repair in G2 Mol. Cell. Biol., May 15, 2003; 23(10): 3692 - 3705. [Abstract] [Full Text] [PDF]
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 F. Cortes and N. Pastor Induction of endoreduplication by topoisomerase II catalytic inhibitors Mutagenesis, March 1, 2003; 18(2): 105 - 112. |
