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.
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.