RBX1 and myelodysplastic syndrome: Furthermore, the role of CK1α in mediating tumor cell survival is supported by the finding that treatment with the immunomodulatory drug (iMID) lenalidomide (Lena) induced the E3 ubiquitin ligase CUL4-RBX1-DDB1-CRBN (CRL4CRBN)-mediated ubiquitination of CK1α in del(5q) myelodysplastic syndromes (MDS), in which one CSNK1A1 allele is lost, with degradation of the residual CK1α protein [22].