Gene expression/regulation homeodomains

Eucaryotes have many more genes and a broader range of specific transcription factors than procaryotes and gene expression is regulated by using sets of these factors in a combinatorial way. Eucaryotes have found several different solutions to the problem of producing a three-dimensional scaffold that allows a protein to interact specifically with DNA. In the next chapter we shall discuss some of the solutions that have no counterpart in procaryotes. However, the procaryotic helix-turn-helix solution to this problem (see Chapter 8) is also exploited in eucaryotes, in homeodomain proteins and some other families of transcription factors. 

Homeodomain proteins Regulate gene expression during development Helix-turn- helix... 

Yamamoto, H., Miyamoto, K., Li, B., Taketani, Y., Kitano, M., Inoue, Y., Morita, K., Pike, J.W., Takeda, E. 1999. The caudal-related homeodomain protein Cdx-2 regulates vitamin D receptor gene expression in the small intestine. J. Bone Min. Res. 14, 240-247. 

The helix-turn-helix motif is found in homeodomain proteins (proteins that play critical roles in the regulation of gene expression during development). 

Genes encoding homeodomain transcriptional regulators are also activated by translocation. In T-ALL, the gene for the Hox-11 transcription factor is expressed ectopically in normal, terminally differentiated effector T-cells. When the Hox-11 gene is expressed. 

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