We found PRMT5 expression was upregulated during HTLV-1-mediated T-cell transformation, as well as in established lymphocytic leukemia/lymphoma cell lines and ATLL patient PBMCs. shRNA-mediated reduction in PRMT5 protein levels or its inhibition by a small molecule inhibitor (PRMT5i) in HTLV-1-infected lymphocytes resulted in increased viral gene expression and decreased cellular proliferation.
Since knockdown of PRMT5 expression or forced expression of HSP90A with alanine replacement of R345 or R386 induced apoptosis with the degradation of client proteins in NDRG2<sup>low</sup> ATL-related and other cancer cells, we here identified that the novel arginine methylations of HSP90A are essential for maintenance of its function in NDRG2<sup>low</sup> ATL and other cancer cells.