THE CONSERVED 3'-FLANKING SEQUENCE, AATGGAAATG, OF THE WHEAT HISTONE H3 GENE IS NECESSARY FOR THE ACCURATE 3'-END FORMATION OF MESSENGER-RNA

We examined the 3'-flanking regions required for accurate 3'-end formation of wheat histone H3 mRNA using gene expression in transformed sunflower cells. The introduction of mutations into the conserved sequence AATGGAAATG in the 3'-flanking region of plant histone genes, located 22 bp upstream from the polyadenylation site of the wheat H3 gene (TH012), completely abolished the 3'-end formation of mRNA at the authentic 3' end without affecting the transcription efficiency. However, a 0.8 kbp sequence containing this motif could not produce a normal 3' end when joined to the 3' end of the nopaline synthase (NOS) gene instead of its 3' sequence. The results indicated that this conserved sequence is necessary but not sufficient for the 3'-end formation of H3 or NOS mRNA. Deletion of a 59 bp sequence, located 19 bp upstream from the AATGGAAATG sequence, also reduced the 3'-end formation efficiency by a factor of 10, compared with the efficiency in wild-type gene. We concluded that 3'-end formation of wheat histone H3 mRNA is regulated by multiple sequences including the AATGGAAATG motif.