Luman Recruiting Factor (LRF)

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