Upstream repressor sequence:  In a general sense, a URS is a cis-acting regulatory element, usually located significantly upstream of the promoter and TATA box, to which repressors bind to silence transcription of nearby genes.

Although the term “URS” can in principle be used to describe any cis-acting upstream sequence that activates transcription, in practice the term silencer is used more often to describe these sequences in a general sense. URS tends to be used to specifically describe the enhancer of the yeast $GAL1$ gene.