A NOVEL GLYCOSAMINOGLYCAN-BINDING PROTEIN IS THE VERTEBRATE HOMOLOG OF THE CELL-CYCLE CONTROL PROTEIN, CDC37

Using a monoclonal antibody, IVd4, that recognizes a novel group of hy aluronan-binding proteins, we have immunoscreened a cDNA library const ructed from embryonic chick heart muscle mRNA. One of the cDNAs isolat ed from the library encodes a 29.3-kDa protein homologous to Cdc37, an essential cell cycle regulatory factor previously characterized genet ically in yeast and Drosophila; this the first vertebrate CDC37 gene t o be cloned to date. We also present evidence for the existence of a s econd chick isoform that is identical to the 29.3-kDa protein over the first 175 amino acids but is entirely different at the carbonyl termi nus and lacks the IVd4 epitope. The avian Cdc37 binds hyaluronan, chro ndroitin sulfate and heparin in vitro, and both isoforms contain glyco saminoglycan-binding motifs previously described in several hyaluronan -binding proteins. These findings suggest a role for glycosaminoglycan s in cell division control.