Cloning and Characterization of the Promoter Region of the Murine Alpha-4 Integrin Subunit

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Abstract
To study the differential expression of the murine VLA-4 (α4β1) integrin, the 5′-flanking region of the gene for the α subunit (α4m) was isolated and a cDNA for α4m was obtained with reverse transcriptase polymerase chain reaction (RT-PCR). The cDNA sequence contained a difference in the signal peptide region compared to the previously described cDNA (Neuhaus et al, 1991). As a consequence, another start codon is predicted, resulting in a decrease in size of the signal peptide. This was confirmed by genomic sequencing. The promoter region was delimited by ribonuclease protection assay (RPA) and transfection experiments fusing 5′-upstream fragments to the luciferase gene. A fragment extending from −936 to +221 was capable of controlling the expected cell-type-specific expression. Sequence comparison of the mouse α4m promoter region with the human α4h promoter revealed little homology. Like most integrin subunits, α4m lacks TATA anc CCAAT boxes. Putative recognition sites for DNA-binding nuclear factors (AP1, AP2, Sp1, and PU1) were identified. The characterization of the promoter region and further identification of the transcription regulatory elements should provide insight in the regulation of α4m integrin gene expression.