Luman Recruiting Factor (LRF)

A novel Luman recruitment factor (LRF). Like Luman, LRF is a UPR responsivebasic-region leucine zipper protein that is prone to proteasomal degradation. Being a highlyunstable protein, LRF interacts with Luman through the leucine zipper region and promotesLuman degradation. LRF was found to recruit the nuclear form of Luman to discrete nuclear focithat overlaps with the nuclear receptor coactivator GRIP1 bodies, and repressed thetransactivation activity of Luman. LRF is a negative regulator of the UPR. For Luman, it may represent another level ofregulation following Luman proteolytic cleavage on the ER and nuclear translocation. Inaddition to inducing Luman rapid turnover, LRF may repress the transactivation potential ofLuman by sequestering it in the LRF nuclear bodies away from key co-factors (such as HCF-1)that are required for transcriptional activation.