The overlap of Inr and TATA elements sets the use of alternative transcriptional start sites in the mouse galectin-1 gene promoter

In the mouse gene encoding the protein galectin-1, transcription initiation at the +1 site is directed by a TATA box. Here we show that a consensus In r element (TCCAGTT), which spans residues -34 to -28 and overlaps the TATA box, directs RNA initiation also from a previously uncharacterized site loc ated at position -31. Upstream transcripts are polyadenylated and contribut e to more than half of the galectin-1 mRNA population in all tissues analyz ed. The promoter architecture is evolutionarily conserved to man, and galec tin-1 mRNA size variants accumulate also in human HeLa cells. The 5 ' end t erminus of the transcripts initiated at residue -31 is extremely GC-rich, a nd may fold into a relative stable hairpin which could influence translatio n and thus modulate the intracellular levels of galectin-1. The interval -6 3/+45 contains sufficient information to ensure RNA initiation from both -3 1 and fl sites, and a Spl site spanning residues -57 to -48 is crucial for promoter functioning. The unusual overlap of core promoter elements suggest s that RNA initiation from the -31 and the fl sites may take place in a seq uential manner. (C) 2001 Elsevier Science B.V. All rights reserved.