Bicoid protein

An interesting case of regulation at the translation level was discovered on the example of the homeodomain protein bicoid (bed), which is important in Drosophila differentiation (Dubnau and Struhl, 1996). The bicoid protein is a transcriptional activator that binds a cognate DNA element and stimulates the transcription of the neighboring genes. Apart from its specific DNA-binding capabUity, the bicoid protein binds to 3 -, non-translating sequences of the mRNA of another homeodomain protein (caudal protein) to inhibit its translation. 

Driever, W. and Nusslein-Volhard, C. The bicoid protein is a positive regulator of hunchback transcription in the early Drosophila embryo (1989) Nature 337,138-143... 

Niisslein-Volhard found that this mRNA is translated soon after fertilization, and the Bicoid protein diffuses through... 

Driever, W. Nusslein-Volhard, C. (1988). A gradient of bicoid protein in Drosophila embryos. Cell 54, 83-93. 

Transcriptional Control by Maternally Derived Bicoid Protein Specifies the Embryo s Anterior... 

Bicoid protein, a homeodomain-type transcription factor, activates expression of certain anterior-specific genes discussed later. In the syncytial fly embryo. Bicoid protein spreads through the common cytoplasm away from the an-... 

Cell types at the posterior end of the fly embryo are controlled by a different mechanism—one in which control is at the translational level rather than the transcriptional level. As just discussed, transcription of the embryo s hunchback gene, which promotes anterior cell fates, produces an anteriorly located band of hunchback mRNA and Hunchback protein because of the anterior posterior gradient of maternally derived Bicoid protein. In addition, however, hunch-... 

Early anterioposterior patterning in Drosophila produces an anterior posterior gradient of Hunchback (Hb), a transcription factor that promotes anterior cell fates. Transcription of the embryonic hb gene is activated by maternally derived Bicoid protein, which is localized to the anterior (see Figure 15-20). 

Figure 3.10 Concentration gradient of bicoid in the developing fruitfly. Concentration of bicoid protein has been measured in developing embryos as a function of location on the anterior-posterior axis. When present at high levels, biocoid protein activates the gene tailless at intermediate levels, inhibits the gene KruppeC, and activates hunchback. Spatial localization of gene expression is thereby achieved with a simple mechanism for protein-gradient formation.

---