A UROCHORDATE PUTATIVE HOMOLOG OF HUMAN EB1, THE PROTEIN WHICH BINDS APC

The human EB1 protein has been cloned by virtue of its interaction wit h the C-terminus of the APC (adenomatous polyposis coli) protein, whos e C-terminal truncated forms have been shown to accompany sporadic and familial forms of colorectal cancer. We have cloned a putative EB1 ho molog from Botryllus schlosseri (Urochordata, Ascidiacea). The deduced protein is 287 amino acids long, and is identical with 48% of the res idues in human EB1 and 24-25% in two yeast hypothetical proteins. We p ropose that such a high degree of conservation among EB1 homologs is i ndicative of an essential regulatory mechanism in eukaryotic cells.