Characterization of two promoters that regulate alternative transcripts inthe microtubule-associated protein (MAP) 1A gene

We cloned and characterized the mouse gene for microtubule-associated prote in (MAP) 1A. an important protein for neuronal morphology and mitotic spind le formation. We also investigated the 5' untranslated region of the gene t o characterize the promoter units. Two alternative transcripts different in the 5' region were identified by 5' RACE. Both transcripts were principall y observed in the brain. Genomic cloning revealed that exons 1. 2, and 4 ge nerate the 5' part of a long transcript, whereas exons 3 and 4 generate a s hort transcript. Putative 5' and intronic promoters flanking exons 1 and 3. respectively, are GC rich and lack a canonical TATA box. DNase I footprint ing from mouse cells revealed that several potential cis-elements were occu pied by nuclear proteins. A reporter assay system in conjunction with a num ber of deletion and mutation constructs was used to test the two putative p romoters. Both putative promoters showed transactivity and their function w as dependent upon Sp1 sites. In addition, an NF-1 site, an HNF3B site. and an AP-1/ATF site were necessary for basal promoter activity of the intronic promoter. Our data provide insight into the regulatory mechanisms that gov ern the expression of the MAP1A gene. (C) 2001 Elsevier Science B.V. All ri ghts reserved.