Transcription restart after a genotoxic challenge is a fundamental yet poorly understood process. Here, we dissect the interplay between transcription and chromatin restoration after DNA damage by focusing on the human histone chaperone complex HIRA, which is required for transcription recovery post UV. We demonstrate that HIRA is recruited to UV-damaged chromatin via the ubiquitin-dependent segregase VCP to deposit new H3.3 histones. However, this local activity of HIRA is dispensable for transcription recovery. Instead, we reveal a genome-wide function of HIRA in transcription restart that is independent of new H3.3 and not restricted to UV-damaged loci. HIRA coordinates with ASF1B to control transcription restart by two independent pathways: by stabilising the associated subunit UBN2 and by reducing the expression of the transcription repressor ATF3. Thus, HIRA primes UV-damaged chromatin for transcription restart at least in part by relieving transcription inhibition rather than by depositing new H3.3 as an activating bookmark.

Transcription restart after a genotoxic challenge is a fundamental yet poorly understood process. Here, we dissect the interplay between transcription and chromatin restoration after DNA damage by focusing on the human histone chaperone complex HIRA, which is required for transcription recovery post UV. We demonstrate that HIRA is recruited to UV-damaged chromatin via the ubiquitin-dependent segregase VCP to deposit new H3.3 histones. However, this local activity of HIRA is dispensable for transcription recovery. Instead, we reveal a genome-wide function of HIRA in transcription restart that is independent of new H3.3 and not restricted to UV-damaged loci. HIRA coordinates with ASF1B to control transcription restart by two independent pathways: by stabilizing the associated subunit UBN2 and by reducing the expression of the transcription repressor ATF3. Thus, HIRA primes UV-damaged chromatin for transcription restart at least in part by relieving transcription inhibition rather than by depositing new H3.3 as an activating bookmark.

Acknowledgments:We warmly thank the patients and their families for their participation in this study. We thank Slimane AIT-SI-ALI for helpful discussions and comments on the manuscript, Anne PLESSIS (Jacques Monod Institute, Paris, France) for helpful discussions on setting the SNAP-TAG technology, Anne VANET (Jacques Monod Institute, Paris, France) for helpful discussions on the HSF2 structural modelling. We thank Lauriane FRITSCH and Slimane AIT-SI-ALI (UMR7216, for HeLa-S3 cells and growth conditions for TAP-TAG analyses). We thank the Imaging Platform IMAGOSEINE and especially Nicole BOGETTO for her help in sorting the GFP-positive HeLa-S3 cells. We are grateful to Heinrich LEONHARDT (Ludwig-Maximilians University, Munich, Germany) for F3H cellular and molecular tools and Pierre-Antoine DEFOSSEZ and Laure FERRY (UMR7216) for helpful guidance in F3H and GFP-Trap experiments, Isabelle LEMASSON (East Carolina University, USA) for the KIX-GST constructs, and Sophie POLO (UMR7216) for SNAP-TAG vectors. We are grateful to Vincent El Ghouzzi for the kind gift of human induced pluripotent stem cells (hIPSCs). We thank Isabelle COUPRY and Benoit ARVEILER (CHU de Bordeaux, France) for primary skin fibroblasts from healthy donors. We thank the Institut Médical Jérôme Lejeune for the gift of Lymphoblastoid cells (patients 4 and 5). We are grateful to Delphine BOHL, and Stéphane BLANCHARD from Pasteur Institute (Rétrovirus et Transfert Génétique, INSERM U622) for their help in producing the retroviruses for TAP-TAG experiments in Hela-S3 cells. We thank Laure FERRY (UMR7216) and the Epigenomics Platform, as well as Sandra PIQUET (UMR7216) and the Microscopy Platform (UMR7216) for access to instruments and technical advice, and Clara GIANFERMI (UMR7216) for microscopy pictures of organoids and nSBs. We thank Isabelle Le PARCO and the staff from the Buffon animal housing facility at the Jacques SUMMARY Cells respond to protein-damaging insults by activating heat shock factors (HSFs), key transcription factors of proteostasis. Abnormal levels of HSFs occur in cancer and neurodegenerative disorders, highlighting the strict control of their expression. HSF2 is a short-lived protein, which is abundant in the prenatal brain cortex and required for brain development. Here, we report that HSF2 is acetylated and co-localized with the lysine-acetyl transferases CBP and EP300 in human brain organoids. CBP/EP300 mediates the acetylation of HSF2 on specific lysine residues, through critical interaction between the CBP-KIX domain and the HSF2 oligomerisation domain, and promotes HSF2 stabilization. The functional importance of acetylated HSF2 is evidenced in Rubinstein-Taybi syndrome (RSTS), characterized by mutated CBP or EP300. We show that cells derived from RSTS patients exhibit decreased HSF2 levels and impaired heat shock response. The dysregulated HSF pathway in RSTS opens new avenues for understanding the molecular basis of this multifaceted pathology.