Search

The Hox11 gene family potentially codifies the evolutionary conserved regulatory factors involved with multicellular integration in Porifera and Metazoa. We are now looking for deep homologies at the level of Hox11 gene regulation. One kilobase upstream of the transcription initiation site of human Hox11, mouse Hox11 and Porifera Hox11 (EmH-3, Ephydatia muelleri, and prox2, Ephydatia fiuviatilis) were aligned (Clustal). We found six putative elements (Transfactor) present in the same position in all the sequences (AP, IK2, CAAT, USF-Q6 LMO2COM, and CEBPB). To test whether these elements play conserved functions among Porifera and Mammalia, seven fragments with different 5' upstream regions of the Emil-3 promoter, ranging from -173 to -538, were fused to the reporter gene Luciferase (Promega); their activity was tested in cell extracts of transiently transfected mammalian cell lineages. The K562, but not 3T3 and HL-60, lineages express endogenous Hox11. The functional test on promoters wase also performed on differentiated K562 (sodium-butyrate) and HL-60 (retinoic acid). The profile of activity of the Emil-3 promoter was independent of the endogenous expression of Hox11 gene, but dependent of the differentiation stage of the cell lineage. The activation of the fragment 7231 (containing the IK element) and the inhibition capacity of the fragment -279 (containing the USF element) were more pronounced in less differentiated cell lineages, indicating a downregulation of IK and USF in differentiated cells. These results also suggest the presence of positive regulatory regions close to the transcription start site of the Hox11 gene (IK and CAAT). (Supported by FAPERJ/FUJB.)