Characterization of the promoter controlling Mona/Gads expression in the megakaryocytic lineage

Mona/grb2 related adapter downstream of shc is a molecular adapter expressed in platelets, T lymphocytes and myelomonocytic cells. Using human hematopoietic cell lines, we have previously shown that lineage-specific Mona expression is achieved through the production of two transcripts (named 1A and 1B) differing by their 5′ untranslated region (5′UTR). Thus, platelets and megakaryocytic cell lines K562 and HEL (Human Erythro-Leukemia) specifically express 1B messenger RNA (mRNA). We report here characterization of the (−2031/+72) genomic region relative to the putative transcription start site of 1B mRNA. We show this region is sufficient to ensure specific reporter gene expression in megakaryocytic cell lines, and that most promoter activity is contained in the (−225/+72) fragment. Electro-mobility shift assay and mutational analyses indicated that GATA-1 and a yet unidentified E-26 family member transcription factor are required for 1B (−2031/+72) promoter activity. Thus, Mona 1B promoter exhibits typical features of megakaryocyte-specific promoters.