1. Volume 57, Issue 3, Pages 492-505 (February 2015)
Interaction of Chk1 with Treslin Negatively Regulates the Initiation of Chromosomal DNA Replication 
Cai Guo, Akiko Kumagai, Katharina Schlacher, Anna Shevchenko, Andrej Shevchenko, William G. Dunphy 
Molecular Cell 
Volume 57, Issue 3, Pages (February 2015)
DOI: /j.molcel
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2. Molecular Cell 2015 57, 492-505DOI: (10.1016/j.molcel.2014.12.003)
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3. Figure 1
Identification of Chk1 as a Treslin-Interacting Protein in Human Cells
(A) Procedure for isolation of Treslin-interacting proteins.
(B) Nuclear lysates from 293T cells expressing tag only (lanes 1 and 5) or indicated forms of Treslin-SF (lanes 2–4 and 6–8) were incubated with S-protein agarose (lanes 1–4). Beads were immunoblotted with anti-TopBP1 (top), anti-Chk1 (middle), and anti-FLAG (bottom). Input lysates, lanes 5–8.
(C) Nuclear lysates from 293T cells were incubated with control immunoglobulin G (IgG; lanes 2, 5, and 8) or antibodies against Chk1 (lanes 3, 9, 10, and 11) or Treslin (lane 6) bound to magnetic beads. In the right panel, bead-bound anti-Chk1 immunoprecipitates (lanes 9–11) were either left on ice (lane 9) or incubated without (lane 10) or with 20 U/μl lambda phosphatase (lane 11) for 30 min at room temperature. Immunoprecipitated proteins and input lysates were immunoblotted for Treslin (top) and Chk1 (bottom). See also Figure S1 and Table S1.
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4. Figure 2 Mapping of the Region in Treslin that Associates with Chk1
(A) Indicated deletion mutants of Treslin were expressed in 293T cells. Nuclear lysates were incubated with S-protein agarose. Bound proteins and nuclear lysates were immunoblotted with anti-Chk1 (top) and anti-FLAG (bottom).
(B) Abilities of various fragments of Treslin to interact with Chk1. Data from (A) and (D); interacting fragments shown in bold.
(C) Amino acids 1,810–1,909 of human Treslin and corresponding portions of the X. laevis and zebrafish proteins were aligned with the Clustal Omega program. Amino acids with asterisks (S1887, S1893, and T1897) or a line (1846-LTQSPLL-1852) were subjected to mutagenesis.
(D) GST only (lane 2), GST-tagged TRCT (lane 3), TRCT containing mutations S1887A (lane 4), S1893A (lane 5), T1897A (lane 6), or 7A (lane 7), and GST-tagged forms of residues 1,810–1,872 (lane 8) and 1,870–1,909 from Treslin (lane 9) were isolated from bacteria with glutathione agarose. Bead-bound fragments were incubated with 293T nuclear lysates. Beads were processed for immunoblotting with anti-Chk1 (top) and staining with Coomassie blue (bottom). Lane 1, input nuclear lysate.
(E) Nuclear lysates from 293T cells expressing SF tag only (lanes 1 and 5) or indicated forms of Treslin-SF (lanes 2–4 and 6–8) were incubated with S-protein agarose. Input lysates (lanes 1–4) and retrieved bead fractions (lanes 5–8) were immunoblotted as indicated. See also Figure S2.
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5. Figure 3
The TRCT Domain Promotes the Phosphorylation of Treslin by Chk1
(A) GST (lanes 1–2), GST-TRCT (lanes 3–4), and versions of this fragment containing the S1887A (lanes 5–6), S1893A (lanes 7–8), T1897A (lanes 9–10), or 7A mutations (lanes 11–12) were incubated with recombinant WT Chk1 (lanes 1, 3, 5, 7, 9, and 11) or KD Chk1 (lanes 2, 4, 6, 8, 10, and 12). See Supplemental Experimental Procedures for more details. Reactions were processed for phosphorimaging (top) and Coomassie blue staining (bottom).
(B) Nuclear lysates from human 293T cells expressing SF tag only (lane 1), full-length Treslin-SF WT (lane 2), or Treslin-SF 7A (lane 3) were processed for purification with anti-FLAG beads. Beads were stained with Coomassie blue.
(C) Control (lanes 1–2), Treslin-SF WT (lanes 3–4), and Treslin-SF 7A (lanes 5–6) were incubated with WT Chk1 (lanes 1, 3, and 5) or KD Chk1 (lanes 2, 4, and 6) in kinase buffer. Reactions were processed for phosphorimaging.
(D) Parental U2OS T-REx cells and T-REx cells harboring either WT or 7A siRNA-resistant Treslin were cultured with doxycycline. Cells were treated with either control or Treslin siRNA. At 72 hr, cells were labeled with 10 μM EdU for 1 hr. EdU incorporation was determined with the Click-iT reaction and Alexa 488 dye (Kumagai et al., 2010). Error bars, mean ± SEM (n = 3).
(E) T-REx cells (lanes 1–4) and T-REx cells harboring siRNA-resistant WT (lanes 5–8) or 7A Treslin (lanes 9–12) were cultured with doxycycline. Cells were also treated with either control siRNA (lanes 1–2, 5–6, and 9–10) or Treslin siRNA (lanes 3–4, 7–8, and 11–12). At 72 hr, cells were incubated in the absence (lanes 1, 3, 5, 7, 9, and 11) or presence (lanes 2, 4, 6, 8, 10, and 12) of 10 μg/ml APH for 30 min. Cell lysates were immunoblotted as indicated. See also Figure S3.
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6. Figure 4
The Isolated TRCT Domain Stimulates DNA Replication in the Xenopus NPE System
(A) HSS was incubated without (lanes 1–2) or with (lanes 3–10) sperm nuclei for 30 min. NPE and either WT (lanes 1, 3, 5, 7, and 9) or 7A TRCT (lanes 2, 4, 6, 8, and 10) were added to HSS. Final concentration of TRCT was 60 ng/μl. Replication was assessed by incorporation of 32P from α-[32P]dATP at the indicated times.
(B) Quantitation of the data from (A) and similar experiments (4–6 total). Results for TRCT WT and 7A were compiled from six independent experiments. Data were normalized to replication in the presence of TRCT WT at 90 min (∗∗∗p < 0.001). Error bars, SEM.
(C) Similar to that in (A), except in some cases NPE was pretreated with 1 μM GST-p27 (lanes 4 and 8).
(D) NPE incubated for 30 min with buffer only (lanes 2, 3, and 6) or 60 ng/μl WT (lanes 4 and 7) or 7A TRCT (lanes 5 and 8). Samples were immunoprecipitated with control IgG (lane 2), anti-Chk1 (lanes 3–5), or anti-Treslin antibodies (lanes 6–8) bound to protein A magnetic beads. Beads were processed for immunoblotting with anti-Treslin (top), anti-TopBP1 (middle), and anti-Chk1 (bottom). NPE (0.5 μl) was loaded in lane 1.
(E) Quantitation of data from seven independent experiments on replication in the NPE system with added buffer alone or 0.5 μM AZD7762. Data were normalized to replication in the presence of AZD7762 at 90 min (∗∗p < 0.01; ∗∗∗p < 0.001). Error bars, SEM. See also Figure S4.
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7. Figure 5
Depletion of Chk1 from Egg Extracts Also Stimulates DNA Replication
(A) Coomassie blue staining of purified GST-TRCT-NLS WT (lane 1) and 7A (lane 2).
(B) Egg extracts containing added buffer only (lane 1) or 75 ng/μl of either WT TRCT-NLS (lane 2) or 7A TRCT-NLS (lane 3) were incubated with sperm nuclei for 90 min. Nuclear lysates were immunoblotted for Treslin (top), Chk1 (middle), and GST (bottom).
(C) Egg extracts were supplemented with buffer only (lanes 1–3), 75 ng/μl WT TRCT-NLS (lanes 4–6), or 7A TRCT-NLS (lanes 7–9). DNA replication was measured at the indicated times.
(D) Quantitation of the data from (C) and two additional experiments (mean ± SEM). Paired Student’s t tests for extracts treated with WT TRCT-NLS versus extracts treated with buffer only or 7A TRCT-NLS yielded p values <
(E) Egg extracts were either mock depleted with control IgG (lane 1) or depleted with anti-Xenopus Chk1 antibodies (lanes 2 and 3). His6-Chk1 was added back to Chk1-depleted extract (lane 3).
(F) The extracts from (E) were assayed for chromosomal DNA replication.
(G) Quantitation of the data from (F) and two additional experiments (mean ± SEM). Paired Student’s t tests for Chk1-depleted extracts versus mock-depleted and Chk1-depleted extracts containing recombinant Chk1 yielded p values < 0.05.
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8. Figure 6
The TRCT Domain Elicits Increased Loading of Cdc45 and Dysregulated Activation of Chk1
(A) HSS was incubated without (lanes 1–2) or with (lanes 3–10) sperm nuclei for 30 min. NPE and either WT (lanes 1, 3, 5, 7, and 9) or 7A TRCT (lanes 2, 4, 6, 8, and 10) at a final concentration of 60 ng/μl were added to HSS. Chromatin was isolated at the indicated times and immunoblotted with various antibodies. Xenopus ISWI served as loading control. NPE/HSS mixture (0.5 μl) was loaded in lanes 9–10.
(B) Similar to that in (A), except NPE was treated with 10 μM actinomycin D as indicated (lanes 5–7).
(C) Distribution of interorigin distances in Xenopus egg extracts containing added buffer alone, TRCT-NLS WT (75 ng/μl), or TRCT-NLS 7A (75 ng/μl). Results are from three independent experiments (mean ± SEM). p < 0.05 for buffer versus WT and for WT versus 7A in the category of 10–15 kb using Student’s t test. p < 0.05 for buffer versus WT and p < 0.001 for WT versus 7A in the category of >30 kb.
(D) HSS was incubated in the absence (lanes 1–6) or presence (lanes 7–14) of sperm nuclei for 30 min. NPE lacking (lanes 1–3, 7–9, and 13) or containing (lanes 4–6, 10–12, and 14) 50 μg/ml APH and buffer (lanes 1, 4, 7, and 10), TRCT WT (lanes 2, 5, 8, 11, 13, and 14), or TRCT 7A (lanes 3, 6, 9, and 12) were added to HSS. Final concentration of TRCT was 60 ng/μl. Mixtures were incubated for 90 min in the absence (lanes 1–12) or presence (lanes 13–14) of 5 mM caffeine. Reactions were immunoblotted with anti-P-Chk1 (top), anti-Chk1 (middle), and anti-GST (bottom). See also Figures S5 and S6.
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9. Figure 7
Overexpression of the Treslin-7A Mutant in Human Cells Elicits Increased Initiation of Replication
(A) Schematic of DNA fiber analysis. Green tracks, CldU; red tracks, IdU. Examples of various types of tracks are depicted.
(B) U2OS T-Rex cells harboring Treslin WT (lanes 1 and 2) or Treslin 7A (lanes 3 and 4) were incubated for 48 hr in the absence (lanes 1 and 3) or presence (lanes 2 and 4) of doxycycline. Cell lysates were immunoblotted as indicated.
(C) U2OS T-Rex cells harboring Treslin WT or Treslin 7A were incubated for 48 hr in the absence or presence of doxycycline. Cells were labeled sequentially with CldU and IdU and processed for preparation of DNA fibers as described in the Experimental Procedures. Images of DNA fibers from doxycycline-treated cells expressing WT or 7A Treslin are shown.
(D) Summary of new origins fired during labeling with IdU. Results for induced WT and 7A cells were compiled from four independent experiments with two different clonal isolates for each construct (p < 0.001). Error bars, SEM.
(E) Model for the Treslin-Chk1 interaction. See Discussion for details. See also Figure S7.
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