Your biotech company is working with a newly discovered fungus, Penicillum novelicus, which synthesizes a tetracycline-type antibiotic called novecycline. Your job is to understand the regulation of expression of the enzymes responsible for synthesis of novecycline, so that it can be optimized for production of the antibiotic. You embark on an extended study of the expression of the enzymes responsible for synthesis of novecycline. The novecycline molecule is the product of a pathway requiring 9 enzymes and its synthesis represents a significant investment of cellular resources. The genes encoding these enzymes are named NO V 1 NO V 9 . As expected, expression of the NO V genes is tightly regulated. Here is what you know about the expression of the NO V gene products under 4 different conditions: 1. They are present at a very low level when P . novelicus is grown in the standard medium. 2. They are present at a high level when muramic acid, a major component of bacterial cell walls, is added to cultures of P . novelicus. Presumably the presence of muramic acid is a signal to the fungus that bacteria are present. 3. They are present at a low level when P . novelicus is grown in standard medium plus muramic acid and high levels of novecycline. 4. They are present at a low level when P. novelicus is grown in standard medium plus muramic acid in the presence of a specific cyanobacterium (photosynthetic bacterium), Synechococcus symbiodinium. This species enters into a symbiotic relationship with P . novelicus, and both the fungus and cyanobacterium grow better in each other's presence, especially in nutrientlimiting conditions. (It is thought that the fungus and cyanobacterium exchange certain nutrients.) While S . symbiodinium can tolerate low levels of novecycline, it stops growing in the presence of high levels of the antibiotic. This regulation likely allows the symbiotic partner of the fungus to survive, so that the symbiosis can take place. The aim of your work is to explain these facts. You will focus on the regulation of NO V 1 , since all the NO V genes behave about the same. The NO V 1 coding region (from start to stop codon) is 1527 bp long - it encodes a polypeptide of 352 amino acid and has 3 introns, all of which are found in the coding region; there are no introns in the predicted untranslated regions (UTRs) of the mRNA. You have cloned the NOV1 coding region along with 1200 bp of DNA upstream and 800 bp downstream of the gene, to include all potential regulatory sites. About 30 bp upstream of the start site of transcription is a predicted TATA box. (See figure below.) When placed on a plasmid that replicates in the fungus, the NOV1 gene is regulated correctly. Elements of the NOV1 gene. The coding region is indicated as a rectangle. The start and stop codons are indicated by "start" and "stop", while the introns are shown as gray boxes. The transcription start site is " + 1 " (corresponds to base 1 of the mRNA) and the TATA box is.