A novel iron responsive element in the 3′UTR of human MRCKα

Human untranslated region (UTR) databases were searched to identify novel proteins potentially regulated by an iron responsive element (IRE), and found two candidates-cell cycle phosphatase Cdc14A variant I and myotonic dystrophy kinase-related Cdc42-binding kinase a (MRCK alpha), both possessing a putative IRE in their 3'UTR. In further experiments, we focused on MRCK alpha. Biochemical analyses of the MRCK alpha IRE revealed that it was functional and mediated the response to iron level in the same way as transferrin receptor I IREs (TfR) did. Similar to TfR mRNA, MRCK alpha,. mRNA is stabilized, when iron supply is low, while it is destabilized under iron-rich conditions. The expression of MRCK alpha, mRNA was found to be ubiquitous; the highest levels were noted in testes, the lowest in skeletal muscle. The level of MRCKa mRNA in various tissues strongly positively correlates with the level of TfR mRNA, indicating its possible role in the transferrin iron uptake pathway. alpha 2006 Elsevier Inc. All rights reserved.