THE ADJACENT YEAST GENES ARO4 AND HIS7 CARRY NO INTERGENIC REGION

The region between the open reading frames of the adjacent yeast genes ARO4 and HIS7 consists of 417 base pairs (bp), Termination of ARO4 tr anscription and initiation of HIS7 transcription has to take place wit hin this interval, because both genes are transcribed into the same di rection, We show that, the ARO4 terminator acid the HIS7 promoter are spatially separated, nonoverlapping units. The ARO4 terminator include s 84 bp of the ARO4 3'-untranslated region with several redundant ARO4 3' end processing signals. Deletion of the ARO4 terminator does reduc e but not completely shut down its expression, The adjacent region of 40 bp is neither required for correct: ARO4 3' end formation nor for H IS7 initiation but contains the nucleotides corresponding to the wild type mRNA 3' ends, The following 280 bp are required for the HIS7 prom oter, Replacement of the housekeeping ARO4 promoter by the stronger AC T1 promoter leads to: reduced HIS7 expression due to transcriptional i nterference, This underlines the compactness of the yeast genome carry ing virtually no intergenic regions between adjacent genes.