Target genes of homeodomain proteins

Homeodomain proteins are transcription factors that share a related DNA bin ding domain, the homeodomain. This class of proteins was first recognized i n the fruitfly Drosophila melanogaster where they cause homeotic transforma tions such as a fly with four wings instead of two (Lewis EB. A gene comple x controlling segmentation in Drosophila. Nature 1978;276:565-570 [Ref. 18] ). They are now known to exist in all eukaryotes where they perform importa nt functions during development. Given that homeodomain proteins are transc ription factors, they control the expression of downstream genes to regulat e development. Which genes are controlled by homeodomain proteins and how m any of them are there? This review focuses on a recent paper by Liang and B iggin (Liang Z, Biggin MD. Eve and Fit regulate a wide array of genes in bl astoderm embryos: the selector homeoproteins directly or indirectly regulat e most genes in Drosophila. Development 1998; 125:4471-4482 [Ref. 1]), whic h proposes that the Drosophila homeodomain proteins Even-skipped and Fushi- tarazu directly control the expression of the majority of genes in the Dros ophila genome. An alternative view, that most genes are only indirectly aff ected by homeodomain proteins is also discussed. BioEssays 21:267-270, 1999 . (C) 1999 John Wiley & Sons, Inc.