Ih. Greger et Nj. Proudfoot, POLY(A) SIGNALS CONTROL BOTH TRANSCRIPTIONAL TERMINATION AND INITIATION BETWEEN THE TANDEM GAL10 AND GAL7 GENES OF SACCHAROMYCES-CEREVISIAE, EMBO journal (Print), 17(16), 1998, pp. 4771-4779
We have investigated transcriptional interactions between the GAL10 an
d GAL7 genes of Saccharomyces cerevisiae. Both genes are part of the g
alactose (GAL) gene cluster which is transcriptionally activated to hi
gh levels in the presence of galactose, Since GAL7 is positioned downs
tream of GAL10 and both genes are expressed co-ordinately at high leve
ls, the possibility that GAL10 transcription influences GAL7 was analy
sed. Using transcriptional run-on assays, we show that high levels of
polymerase are found in the 600 bp GAL10-7 intergenic region that accu
mulate over the GAL7 promoter. Furthermore, GAL7 transcription is enha
nced when the GAL10 upstream activating sequence (UAS(G)) is deleted,
indicating that interference between GAL10 and GAL7 is likely to occur
in the chromosomal locus. Deletions in the GAL10 poly(A) signal resul
t in complete inactivation of the GAL7 promoter and cause a dramatic i
ncrease in bi-cistronic GAL10-7 mRNA, predominantly utilizing the down
stream, GAL7 poly(A) site. These data demonstrate a pivotal role for t
he GAL10 poly(A) site in allowing the simultaneous expression of GAL10
and GAL7, In effect, this RNA processing signal has a direct influenc
e on both transcriptional termination and initiation.