EXPRESSION AND CHARACTERIZATION OF THE LAMININ-BINDING PROTEIN IN HYDRA

Recently, a cDNA was isolated from hydra with extensive homology to a mammalian and invertebrate gene which codes for a protein called lamin in binding protein (LBP). In this paper we describe the protein expres sion of the hydra LBP in Escherichia coli. On SDS gels the recombinant hydra LBP displayed an apparent molecular mass of 43 kDa, although th e calculated mass, including six additional histidines, is 33.7 kDa. P olyclonal antibodies were produced against the hydra recombinant LBP. The antiserum reacted with a 42-kDa and a 43-kDa protein from Hydra vu lgaris and from a multiheaded mutant of Chlorohydra viridissima, respe ctively. In hydra, LBP RNA and protein were highly expressed in cells with short cell cycles, such as all cells of the interstitial cell lin eage, less in slowly cycling epithelial cells, and at very reduced lev els or not at all in differentiated cells. Higher expression in the mu ltiheaded mutant of C. viridissima than in H. vulgaris, the cells of w hich differ in doubling time, hint at a function in cell proliferation . This is supported by the finding that in vitro hydra LBP is a substr ate for the cell-cycle-specific kinase CDC2.