JAK2 V617F, PRMT5, and GATA-1 Form a Regulatory Loop That Controls Autophagy Via Effects on ATG3 Gene Expression

Abstract 2822

The JAK2 V617F mutation is the most prevalent genetic abnormality in Philadelphia chromosome negative myeloproliferative neoplasia. We recently discovered that JAK2 V617F phosphorylates and inactivates PRMT5, a type II arginine methyltransferase that promotes transcriptional repression. To evaluate the PRMT5 dependent and independent effects of JAK2 V617F, we performed microarray analysis of human erythroleukemia cells (homozygous for JAK2 V617F) treated with a JAK2 inhibitor or transduced with PRMT5 shRNA. We discovered 5 autophagy-related genes (ATG3, ATG7, ATG2B, ATG5, and ATG16L1) that were positively regulated by JAK2 V617F, but negatively regulated by PRMT5. PRMT5 was bound to the promoters of these genes and binding was enhanced when PRMT5 was re-activated by a JAK2 inhibitor. Sequence analysis of ATG promoters identified at least one potential GATA-1 binding site in each ATG gene. Yet, knock-down of GATA-1 decreased the expression of ATG3 (by approximately 50%), but not the other ATG genes. ChIP analysis identified binding of both GATA-1 and PRMT5 to the ATG3 promoter, which suggests that ATG3 is transcriptionally induced by GATA-1 when PRMT5 is inactivated by JAK2 V617F. But when PRMT5 was active, it was bound to the GATA-1 promoter and ATG3 expression was downregulated. As JAK2 V617F (but not wild type) induces ATG3 expression and autophagy in AML cells and ATG3 levels are elevated in CD34+ cells from polycythemia vera patients, we conclude that JAK2 V617F promotes autophagy by inactivating PRMT5 and promoting GATA-1-dependent transcription of ATG3. Targeting autophagy with JAK2 inhibitors or other agents may be efficacious in the treatment of myeloproliferative neoplasia.