Abstract 353: Using cancer-associated variants to dissect functions of SETD8

Protein lysine methyltransferases (PKMTs) play important roles in carcinogenesis through methylation of histone and non-histone substrates. SETD8 is the sole human methyltransferase for the monomethylation of histone H4 Lys20 (H4K20me1). Besides histone substrates, SETD8 modifies multiple non-histone substrates including proliferating cell nuclear antigen (PCNA), Numb, and p53. The biological functions related to the methyltransferase activity of SETD8 have been implicated in many essential biological processes including DNA replication, DNA damage response, cell cycle regulation, and transcription modulation. The SET domain of SETD8 is required to catalyze the methylation in substrates using the cofactor S-adenosyl-L-methionine (SAM). The C-terminal region post the SET domain (cSET) contains both the cofactor and protein substrate-binding sites. Recent genomics data from samples of cancer patients have revealed distinct variants in the SET domain of SETD8. Missense mutations, such as, E289Q, R292L, V315I, and H347Q were found in multiple types of cancers. To help dissect the roles of SETD8, we proposed the identification and characterization of SETD8 variants with partial loss-of-function phenotypes. Our data showed that overexpression of the SETD8 mutants increased the migration and tumor sphere formation of breast cancer cells without affecting H4K20me1. In vitro biochemical assay also confirmed that the SETD8 mutants lose the methyltransferase activity on H4K20 substrate. The RNA-seq data in the context of SETD8 mutant indicated that the c-Myc pathway was upregulated without affecting c-Myc expression. With the technology of Bioorthogonal Profiling of Protein Methylation (BPPM), we have found that SETD8 can methylate cancer-associated transcription factors in a cellular context. Collectively, these findings suggest that native SETD8 can act on cancer driving-associated transcription factors and its mutant maintains this methyltransferase activity but spare H4K20 methylation for cancer malignancy. Acknowledgements: This project was supported by 1R01GM120570. Citation Format: Yongxia Zhu, Lihui Wang, Chamara Senevirathne, Shi Chen, Fabio Pittella Silva, Minkui Luo. Using cancer-associated variants to dissect functions of SETD8 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 353.