Nature - USA (2020-01-23)

2

nature research | reporting summary

October 2018

Field-specific reporting

Please select the one below that is the best fit for your research. If you are not sure, read the appropriate sections before making your selection.

Life sciences Behavioural & social sciences Ecological, evolutionary & environmental sciences

For a reference copy of the document with all sections, see nature.com/documents/nr-reporting-summary-flat.pdf

Life sciences study design

All studies must disclose on these points even when the disclosure is negative.

Sample size No statistical methods were used to predetermine sample sizes. Sample sizes were determined based on previous experience.

Data exclusions No data was excluded from the analysis.

Replication All experiments were reliably reproduced. Each experiment was performed independently at least two times, but usually many more times.

Randomization Mice were paired based on gender and age.

Blinding Blinding was not performed due to the unambiguous nature of measurements and systematic analyses used in these experiments.

Reporting for specific materials, systems and methods

We require information from authors about some types of materials, experimental systems and methods used in many studies. Here, indicate whether each material,

system or method listed is relevant to your study. If you are not sure if a list item applies to your research, read the appropriate section before selecting a response.

Materials & experimental systems

n/a Involved in the study

Antibodies

Eukaryotic cell lines

Palaeontology

Animals and other organisms

Human research participants

Clinical data

Methods

n/a Involved in the study

ChIP-seq

Flow cytometry

MRI-based neuroimaging

Antibodies

Antibodies used For WB, ChIP, ChIP-seq:

Anti-H2A.Z, Abcam, ab4174, for WB , ChIP, ChIP-seq;

Anti-H4, Millipore, #05-858, for WB;

Anti-Flag, Sigma, s7452,for WB;

Anti-ORC1, Abcam, ab60, for WB;

Anti-ORC2, Abcam, ab68348 for WB;

Anti-MCM2, Abcam, ab4461, for WB;

Anti-RPA, Abcam, ab79398, for WB;

Anti-H4K20me1, Abcam, ab9051, for WB and ChIP-seq;

Anti-H4K20me2, Abcam, ab9052, for WB, ChIP and ChIP-seq;

Anti-H4K20me3, Abcam, ab9053, for WB and ChIP-seq;

Anti-Suv420H1, Novus, NBP1-78303, for WB;

Anti-tublin, Abcam, ab6046, for WB;

Anti-His, Invitrogen, MA1-21315, for WB;

Anti-H3, Cell signaling, #9715, for WB.

For flow cytometry

1.FFor Surface staining of mouse splenocytes

CD3 FITC (Clone: 145-2C11; Cat. 11-0031-82; Lot:4338511; eBioscience)

B220 PE (Clone: RA3-6B2; Cat. 12-0452; Lot: E01249-1634; eBioscience)

Anti-Brdu FITC (Clone: B44; Cat. 347583; Lot: 6090520; BD)

Live/Dead (Cat. L34959; Lot: 1921586; invitrogen)

2. For T cell Isolation and the analysis of proliferation and cell cycle
   CD4 PerCp-Cy5.5 (Clone: RM4-5; Cat. 45-0042; Lot: 4304295; eBioscience)
   CD8 APC (Clone: 53-6.7; Cat. 17-0081; Lot: E07057-1635; eBioscience)