The SV40 core sequence functions as a repressor element in yeast.

Our previous studies showed that the AP-1 recognition element (ARE) present within the SV40 72-base pair (bp) enhancer will activate transcription in yeast when placed upstream of a truncated CYC1 promoter. However, the AP-2/AP-3 recognition element (also known as the core sequence TGTGGAAAG) from the SV40 enhancer was not able to activate CYC1-dependent transcription. In this report, we show that the core sequence, when cloned next to a yeast UAS (upstream activation sequence), can inhibit the transcriptional stimulatory activity of the UAS. We refer to this sequence as the upstream repressor element (URE) in yeast. Repression occurs in an orientation-independent fashion and irrespective of the placement of the URE between the UAS and TATA box or upstream of both of these elements. Furthermore, repression is seen when the URE is separated from the UAS by up to 214 bp. Interestingly, multiple copies of an activator site can overcome this repression. Gel-shift analysis and URE-probed proteins blots indicate the presence of two polypeptide chains capable of binding the URE in yeast. The experimental evidence suggests that either the repression associated with the URE sequence is mediated by a direct, one-to-one interaction between the proteins recognizing the URE and GCRE, or alternatively, that there is a direct interaction between the activator and repressor for a general transcription factor.