Sequences in the pea rbcS-3A gene have homology to constitutive mammalian enhancers but function as negative regulatory elements.

The pea rbcS-3A gene, which codes for a key component of the photosynthetic machinery, requires light for its expression. Analysis of chimeric constructs in transgenic tobacco plants has shown that a 280-bp fragment from the 5' noncoding region can act as a light-inducible transcriptional enhancer. Further characterization of this enhancer identifies a 58-bp sequence containing two regulatory elements that can decrease transcription in the dark. One has a high degree of homology to the SV40 core enhancer, the other to the adenovirus 5 E1A enhancer and the constitutive part of the human interferon-beta gene enhancer. Deletion of the 58-bp sequence uncovers additional light-responsive elements (LREs) located further upstream and downstream.