HIRA loss transforms FH-deficient cells

Fumarate Hydratase (FH) is a mitochondrial enzyme that catalyses the reversible hydration of fumarate to malate in the TCA cycle. Germline mutations of FH lead to HLRCC, a cancer syndrome characterised by a highly aggressive form of renal cancer( [1][1] ). Although HLRCC tumours metastasise rapidly, FH-deficient mice develop premalignant cysts in the kidneys, rather than carcinomas ( [2][2] ). How Fh1 -deficient cells overcome these tumour suppressive events during transformation is unknown. Here, we perform a genome-wide CRISPR/Cas9 screen to identify genes that, when ablated, enhance the proliferation of Fh1 -deficient cells. We found that the depletion of HIRA enhances proliferation and invasion of Fh1 -deficient cells in vitro and in vivo . Mechanistically, Hira loss enables the activation of MYC and its target genes, increasing nucleotide metabolism specifically in Fh1 -deficient cells, independent of its histone chaperone activity. These results are instrumental for understanding mechanisms of tumorigenesis in HLRCC and the development of targeted treatments for patients. ### Competing Interest Statement C.F. is an adviser for Istesso. G.D.S. has educational grants from Pfizer, AstraZeneca and Intuitive Surgical; consultancy fees from Pfizer, Merck, EUSA Pharma and CMR Surgical; Travel expenses from Pfizer and Speaker fees from Pfizer. [1]: #ref-1 [2]: #ref-2