In the lac operon, lactose binds to the repressor protein and prevents it from repressing gene transcription, while in the trp operon, tryptophan binds to the repressor protein and enables it to repress gene transcription.
42.
As the structure of the lactose-repressor protein shows, she said, such interactions " may involve bending and protein folding and unfolding that you don't see unless you get up close and personal with the protein ."
43.
A repressor protein may have regions that bind to the DNA sequence as well as regions that bind to the transcription factors assembled at the promoter of the gene which would create a chromosome looping mechanism.
44.
Brent's use of prokaryotic repressor proteins and use of them in chimeric proteins to regulate gene expression in eukaryotes was the subject of basic patents ( including, Regulation of Eukaryotic Gene Expression, with Mark Ptashne ).
45.
In 2005, Andrews shelved Sierra Sciences'efforts to identify the telomerase repressor protein, instead switching to the " brute force " strategy of developing assays to screen large numbers of semi-random chemicals to determine whether they induced telomerase.
46.
In particular, his research focused on the phenomenon of catabolite repression, a regulatory system involving interactions of cyclic AMP, the catabolite repressor protein ( CRP ) complex, and the lac operon and other inducible systems in bacteria.
47.
"' RyhB RNA "'is a 90 nucleotide non-coding RNA that down-regulates a set of iron-storage and iron-using proteins when iron is limiting; it is itself negatively regulated by the ferric uptake repressor protein, Fur ( Ferric uptake regulator ).
48.
The operator is the binding site for the repressor and thus has a function equivalent to the silencer region in Eukaryotic DNA . When a repressor protein is bound to the operator, RNA polymerase cannot bind to the promoter to initiate the transcription of the operon.
49.
This mediator complex regulated gene expression by bridging interaction between RNA polymerase II and gene-specific regulating proteins such as transcription factors, repressor proteins, activator proteins, etc . Changes to this complex and the proteins associated can have a severe impact on the production of new proteins.
50.
Brent's use of prokaryotic repressor proteins in eukaryotes, and development of chimeric proteins containing prokaryotic DNA binding domains, enabled identification of other transcription regulatory domains and gene regulatory technologies including tetracycline-repressor controlled transcriptional repression and the Gal4 and LexA UAS systems used in other model organisms.
