Robert S. Sparks
Regulation of Gene Expression
We are interested in mechanisms of regulation of developmental gene expression. Our current focus is to understand how the ornithine decarboxylase gene expression is regulated during embryogenesis in Musca domestica.
Our results have shown that the embryonic ornithine decarboxylase gene is transcribed just after gastrulation, at the time when embryo transcription begins. Also, PCR data suggest that a maternal mRNA is present prior to zygote expression, but is apparently not translated. Western blot analyses, with a heterologous antiserum show that translation of ODC mRNA occurs just after mRNA synthesis. However, the ODC protein is in an inactive form until just prior to hatching of the embryos at about 8 hours post-gastrulation. The appearance of active ODC is at the time of egg hatching, and the activity and protein are rapidly eliminated just after hatching. The conversion of inactive to active ODC does not involve dramatic alterations in the protein primary sequence. The inactive and active proteins are the same size on SDS-PAGE. We have cloned and sequenced the ODC gene from Musca domestica. Sequence analyses show the presence of a casein-kinase phosphorylation consensus sequence, suggesting that a phosphorylation event may be involved in conversion of inactive to active ODC.