Abstract
Previous evolutionary study of the tumor suppressor Merlin revealed that this protein family was produced by very early metazoans with the exception of some or all flatworm lineages [Golovnina et al., 2005]. We ask whether other tumor-suppressor proteins had also been in existence in these times and focus our attention on hyperplastic discs (Hyd) protein, a classic tumor suppressor in Drosophila melanogaster which, when mutated, may cause over-proliferation and malignancy. Phylogenetic analysis of the Hyd protein indicates that it was present among metazoa by the time Trichoplax adhaerens had emerged from the common unicellular ancestor of the Animalia.
