Characterization of the mouse myeloid-associated differentiation marker (MYADM) gene: promoter analysis and protein localization.

Hematopoietic differentiation is a complex process involving many genes inducing functional changes and characteristics of different cell lineages. To understand this process, it is important to identify genes involved in lineage commitment and maturation of hematopoietic progenitor cells. Recently we isolated the novel gene MYADM which is strongly up-regulated as multipotent progenitor cells differentiate towards myeloid cells. Because it is not expressed in lymphocytes, understanding the transcriptional control of MYADM could further explain differences in gene expression between myeloid and lymphoid cells. To identify regulatory elements controlling its restricted expression, we have analyzed the 5'-flanking region of the MYADM gene. The proximal promoter was found to lack both TATA and CCAAT boxes, but contained several potential binding sites for both ubiquitous and myeloid-specific transcription factors. Maximal promoter activity was contained within 800 bp from the tentative transcription initiation site, which was reduced as portions of the 5'-end were deleted, and completely abolished when the transcription initiation site was deleted. This promoter sequence had higher activity in myeloid cells compared to B cells, and activity was enhanced during myeloid differentiation, suggesting that we have identified the MYADM core promoter. Computer predictions had suggested MYADM to encode a protein with multiple transmembrane domains. By immunofluorescence and confocal microscopy we demonstrate that the protein is localized to the nuclear envelope and to intracytoplasmic membranes, indicating that MYADM constitutes an integral membrane protein.