RAD51B and juvenile idiopathic arthritis: SNPs in the promoter region of ZFP36L1 are independently associated with JIA but not RA; however, the interaction of the ZFP36L1 promoter with the RA-associated SNPs suggests that the causal gene in both diseases may be ZFP36L1 and not RAD51B. ZFP36L1 is a zinc finger transcription factor involved in the transition of B cells to plasma cells and it is noteworthy that the interaction with the RA-associated region was only seen in the B-cell line (Fig. 5b).