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Published December 10, 2015 | Accepted Version + Supplemental Material
Journal Article Open

The histone chaperone CAF-1 safeguards somatic cell identity

Abstract

Cellular differentiation involves profound remodelling of chromatic landscapes, yet the mechanisms by which somatic cell identity is subsequently maintained remain incompletely understood. To further elucidate regulatory pathways that safeguard the somatic state, we performed two comprehensive RNA interference (RNAi) screens targeting chromatin factors during transcription-factor-mediated reprogramming of mouse fibroblasts to induced pluripotent stem cells (iPS cells). Subunits of the chromatin assembly factor-1 (CAF-1) complex, including Chaf1a and Chaf1b, emerged as the most prominent hits from both screens, followed by modulators of lysine sumoylation and heterochromatin maintenance. Optimal modulation of both CAF-1 and transcription factor levels increased reprogramming efficiency by several orders of magnitude and facilitated iPS cell formation in as little as 4 days. Mechanistically, CAF-1 suppression led to a more accessible chromatin structure at enhancer elements early during reprogramming. These changes were accompanied by a decrease in somatic heterochromatin domains, increased binding of Sox2 to pluripotency-specific targets and activation of associated genes. Notably, suppression of CAF-1 also enhanced the direct conversion of B cells into macrophages and fibroblasts into neurons. Together, our findings reveal the histone chaperone CAF-1 to be a novel regulator of somatic cell identity during transcription-factor-induced cell-fate transitions and provide a potential strategy to modulate cellular plasticity in a regenerative setting.

Additional Information

© 2015 Macmillan Publishers Limited. Received 23 February 2015; Accepted 28 September 2015. Published online 09 December 2015. We thank B. Kingston, C. Vakoc, M. Tolstorukov and G. Hannon for guidance and discussions, B. Bernstein, K. Plath, K. Chronis, Y. Shen and O. Tam for advice on the ATAC-seq analysis, P. Brown for providing the Dot1l inhibitor, B. Stillman for sharing the Chaf1b antibody and T. Graf for sharing the C10 cell line. We thank C. Nakada and Y. Kiyota (Nikon) for providing software to quantify iPS cell formation and A. Huebner for help with transdifferentiation experiments. We are grateful to H. Hock and the HSCI-CRM flow cytometry core for help with flow data analysis and to W. Mallard for initial RNA-sequencing analysis. We further thank B. Ma, S. Muller, M. Weissenboeck and the IMP/IMBA Biooptics and Transgenic core facility as well the CSF NGS laboratory for technical assistance and all members of the Hochedlinger, Zuber, Penninger, Elling, Shi and Kingston laboratories for their feedback on various aspects of this project. We thank A. Stark, A. Deaton and L. Barrett for critical reading of the manuscript. S.C. was supported by the PRCRP at the Department of Defense (CA 120212). H.Y.C. by was supported by NIH P50-HG007735. U.E. was funded by grants from IMBA and the Austrian National Foundation. S.W.L. was supported by a cancer center support grant and program project grant from the NCI and is an HHMI investigator. J.M.P. was supported by IMBA, ERC GA (number 341036) and the Innovator Award/Era of Hope Award Number W81XWH-12-1-0093. J.Z. was funded by an ERC starting grant (number 336860) and generous institutional funding from Boehringer Ingelheim. K.H. was supported by funds from the MGH, HHMI, NIH (R01 HD058013-06) and the Gerald and Darlene Jordan Chair in Regenerative Medicine. Author Contributions: Y. L. Jung and B. Hopfgartner contributed equally to this work. S.C., K.H., U.E. and J.Z. designed primary screens, analysed and interpreted data. S.C., J.M. and N.A. performed the arrayed screen and S.C. conducted follow-up cell biology and chromatin studies. U.E. and B.H. performed the multiplexed screen. U.E. performed validation experiments, genetic interaction assays and cell biology experiments with support from B.H., M.H. and D.W. Human reprogramming experiments were performed by S.C. and J.B.; N.T. and S.W.L. assisted in the generation of inducible Col1a1::tetOP-Chaf1a shRNA cell lines. S.C., A.I.B., A.B. and Y.S. performed B-cell to macrophage conversion experiments. C.E.A. and M.W. conducted MEF to induced neuron transdifferentiation experiments. Y.L.J., M.N., A.A., F.F. and P.J.P. performed bioinformatics analyses. M.H. and U.E. conducted the CiA assay with support from O.B. D.J.W. assisted with the SONO-seq experiments and H.Y.C. helped with the ATAC-seq assay. J.M., M.H. and M.Z. assisted with western blot and chromatin studies. D.T. and J.R. conducted ChIP experiments and library construction. M.S. and S.E.V. provided secondary Oct4–tdTomato MEFs. J.Z. and S.W.L. provided the arrayed library. J.Z. and P.R. designed the extended chromatin library. M.F., J.J. and B.H. generated lentiviral vectors and RNAi reagents. J.M.P. and G.A. provided intellectual support and mentoring. K.H., S.C., J.Z. and U.E. wrote the paper with input from all co-authors. The authors declare no competing financial interests. All SONO-seq, ATAC-seq, ChIP-seq, RNA-seq and microarray data have been deposited in the Gene Expression Omnibus database under accession number GSE66534.

Attached Files

Accepted Version - nihms-726948.pdf

Supplemental Material - nature15749-s1.pdf

Supplemental Material - nature15749-s2.xlsx

Supplemental Material - nature15749-s3.xlsx

Supplemental Material - nature15749-s4.xlsx

Supplemental Material - nature15749-s5.xlsx

Supplemental Material - nature15749-s6.xlsx

Supplemental Material - nature15749-sf1.jpg

Supplemental Material - nature15749-sf2.jpg

Supplemental Material - nature15749-sf3.jpg

Supplemental Material - nature15749-sf4.jpg

Supplemental Material - nature15749-sf5.jpg

Supplemental Material - nature15749-sf6.jpg

Supplemental Material - nature15749-sf7.jpg

Supplemental Material - nature15749-sf8.jpg

Supplemental Material - nature15749-sf9.jpg

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Additional details

Created:
August 22, 2023
Modified:
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