Friday, April 4, 2008

“Bioinformatic and molecular biological approaches to identifying Id2 promoter sequences required for transcriptional regulation”
 Gilson Sanchez, BIOMED PREP Scholar

Id helix-loop-helix (HLH) proteins play a key role in the regulation of cellular growth and differentiation.  Specifically, Id proteins serve as negative regulators of gene expression and differentiation by sequestering basic HLH transcriptional regulatory factors.  Indeed, Id2 has been found to be up-regulated in some cancers.  Both Id1 and Id2 are expressed in cycling pre-muscle C2C12 cells, but are down-regulated at the level of mRNA accumulation in differentiating cells.  Transient transfection assays to study Id2 promoter activity have shown that sequences to -2250 are insufficient to direct the necessary transcriptional regulation.  Use of FamilyRelations software to compare sequences of Id2 gene promoters across species from human to sea urchin revealed a set of four highly conserved motifs that are located between -2846 and -2629 in the mouse Id2 gene.  CisTematic analysis showed that two of these motifs are also found upstream of the human Id1 gene.  Incorporation of the mouse upstream Id2 promoter fragment to -4331 revealed a five fold increase in the activation of the reporter gene when compared to the activity of the -2250 Id2 reporter vector.  An Id1 reporter construct including the two intergenic conserved sites was shown to decrease in activity by 61 % after cell differentiation.  These findings suggest common and unique mechanisms for regulation of expression of Id1 and Id2 genes in both normal and cancer cells.

Supported by CSU-LSAMP from NSF Grant HRD-0331537 and the CSU Chancellor’s Office.