InterPro domain: IPR006861

This entry represents a domain found in the HABP4 protein family of hyaluronan-binding proteins, and the PAI-1 mRNA-binding protein, PAI-RBP1. HABP4 has been observed to bind hyaluronan (a glucosaminoglycan), but it is not known whether this is its primary role in vivo . It has also been observed to bind RNA, but with a lower affinity than that for hyaluronan [ 1 ]. PAI-1 mRNA-binding protein specifically binds the mRNA of type-1 plasminogen activator inhibitor (PAI-1), and is thought to be involved in regulation of mRNA stability [ 2 ]. However, in both cases, the sequence motifs predicted to be important for ligand binding are not conserved throughout the family, so it is not known whether members of this family share a common function.

Hyaluronan/mRNA-binding protein may be involved in nuclear functions such as the remodeling of chromatin and the regulation of transcription [ 3 , 4 ].

1. Molecular characterization of a novel intracellular hyaluronan-binding protein. J. Biol. Chem. 275, 29829-39
2. Identification and cDNA cloning of a novel RNA-binding protein that interacts with the cyclic nucleotide-responsive sequence in the Type-1 plasminogen activator inhibitor mRNA. J. Biol. Chem. 276, 3341-7
3. Ki-1/57 interacts with RACK1 and is a substrate for the phosphorylation by phorbol 12-myristate 13-acetate-activated protein kinase C. J. Biol. Chem. 279, 11444-55
4. Evidence for the interaction of the regulatory protein Ki-1/57 with p53 and its interacting proteins. Biochem. Biophys. Res. Commun. 341, 847-55