Abstract 2395 HDAC11's de-fatty acylation of SF3B2 could provide new understanding of RNA splicing regulation and Liver Cancer progression

Liver cancer is the world's leading cause of cancer deaths and lacks effective tumor intrinsic treatment avenues. In liver cancer patients, histone deacetylase 11 (HDAC11) is prognostic towards patient death, and HDAC11 has established importance in liver cancer progression and drug resistance. Our study aims to increase the understanding of HDAC11 in liver cancer by applying HDAC11 inhibitors to liver cancer cells and investigating the lysine de-fatty acylation function of HDAC11. It was found that HDAC11 inhibitors slowed cell growth in colony formation and cell viability assays, and in a xenograft model of liver cancer, HDAC11 knockdown completely prevented tumor formation. HDAC11 is a lysine fatty acyl (KFA) hydrolase, or an enzyme that removes KFA (de-KFA) from proteins. However, HDAC11 has few known substrates. The RNA splicing factor SF3B2 was identified as a potential substrate of HDAC11 via analysis of published mass spectrometry datasets. SF3B2 was found to be lysine fatty acylated in HEK-293T and in liver cancer cells, and after treating cells with an HDAC11 inhibitor, SF3B2's KFA increased, indicating that de-KFA of SF3B2 is under regulation of HDAC11. SF3B2 regulates RNA splicing by binding the intronic region before target exons. Androgen receptor variant 7 (ARv7), which is a bona fide target of SF3B2, has been implicated in liver cancer, and we show that the ARv7 splicing pattern is altered with HDAC11i. Furthermore, in the CD44 gene, which is a liver cancer stem cell marker, we show that intronic regions are saturated with SF3B2 binding sites, and that CD44 variant exons are variably included after HDAC11 inhibition. These results indicate that splicing of genes that are important towards liver cancer progression is influenced by HDAC11, and that de-KFA of SF3B2 may be the mechanism by which this occurs. We would like to acknowledge our funding sources that supported this work: R01 CA240529-02 and R01 AI153110-02.