RNA-binding protein HuR regulates nuclear import of protein.

The RNA-binding protein HuR binds to elements rich in adenylate and uridylate (AU-rich elements) in target mRNAs and stabilizes them against degradation. The complete spectrum of genes whose expression is regulated by HuR and are the basis for the broad range of cellular functions of the protein is incompletely understood. We show that HuR controls the expression of multiple components of the nuclear import machinery.

Cellular retinoic acid-binding protein 2 inhibits tumor growth by two distinct mechanisms.

Cellular retinoic acid-binding protein 2 (CRABP2) potently suppresses the growth of various carcinomas, but the mechanism(s) that underlies this activity remains incompletely understood. CRABP2 displays two distinct functions. The classical function of this protein is to directly deliver retinoic acid (RA) to RA receptor (RAR), a nuclear receptor activated by this hormone, in turn inducing the expression of multiple antiproliferative genes.

Transcript stabilization by the RNA-binding protein HuR is regulated by cellular retinoic acid-binding protein 2.

The RNA-binding protein HuR binds at 3' untranslated regions (UTRs) of target transcripts, thereby protecting them against degradation. We show that HuR directly interacts with cellular retinoic acid-binding protein 2 (CRABP2), a protein known to transport RA from the cytosol to the nuclear retinoic acid receptor (RAR). Association with CRABP2 dramatically increases the affinity of HuR toward target mRNAs and enhances the stability of such transcripts, including that of Apaf-1, the major protein in the apoptosome.

Cross talk between signaling and vitamin A transport by the retinol-binding protein receptor STRA6.

The plasma membrane protein STRA6 transports vitamin A from its blood carrier retinol binding protein (RBP) into cells, and it also functions as a cytokine receptor which activates JAK/STAT signaling. We show here that, unlike other cytokine receptors, phosphorylation of STRA6 is not simply induced upon binding of its extracellular ligand. Instead, activation of the receptor is triggered by STRA6-mediated translocation of retinol from serum RBP to an intracellular acceptor, the retinol-binding protein CRBP-I.