NUCLEOTIDE-SEQUENCE OF THE HISTONE GENE-CLUSTER IN THE CORAL ACROPORA-FORMOSA (CNIDARIA, SCLERACTINIA) - FEATURES OF HISTONE GENE STRUCTUREAND ORGANIZATION ARE COMMON TO DIPLOBLASTIC AND TRIPLOBLASTIC METAZOANS

We report the nucleotide sequence of the core histone gene cluster fro m the Cnidarian Acropora formosa. This is the first histone gene clust er to be sequenced from a diploblastic organism and the predicted amin o acid sequences most resemble those of sea urchin equivalents. Each o f the Cnidarian histone genes has two conserved regions 3' of the codi ng sequences and these closely resemble those of the metazoan alpha-cl ass histone genes. In A. formosa the core histone genes are arranged a s opposed (H3/H4 and H2A/H2B) pairs, a pattern common to the nondeuter ostome metazoa, and tandem repetition is the predominant pattern of or ganization in the Cnidarian. With the recent identification of several classes of homeobox genes in Cnidarians these features clearly align the Cnidaria with triploblastic metazoans, supporting a monophyletic o rigin of the metazoa.