We isolated and mapped three new human homeoboxes located on chromosome 2 upstream from the reported seven HOX4 homeobox sequences. Two of them, HOX4I and HOX4H, clearly belong to the HOX gene family, in particular to homology groups 1 and 2, and possibly represent the most 5′ HOX4 homeoboxes. A third homeobox 13 kb upstream from HOX4I was identified. Sequencing data show that this is the human homolog of the murine Evx-2 homeobox. Both homeoboxes are closely related to the murine Evx-1 and to the frog Xhox-3 homeoboxes. The four genes represent vertebrate homologs of Drosophila evenskipped (eve), a segmentation gene of the pair-rule class. Human EVX2 sequences belong to an active gene because they are transcribed and properly processed in cells and tissues. We have identified for the first time a homeogene of a different class at a HOX locus. These findings are relevant to the understanding of the evolution of HOX gene clusters and their regulation.
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