Search results
Results From The WOW.Com Content Network
The LexA repressor or LexA (Locus for X-ray sensitivity A) [1] is a transcriptional repressor (EC 3.4.21.88) that represses SOS response genes coding primarily for error-prone DNA polymerases, DNA repair enzymes and cell division inhibitors. [2]
The activated form of RecA interacts with the LexA repressor to facilitate the LexA repressor's self-cleavage from the operator. [7] [8] Once the pool of LexA decreases, repression of the SOS genes goes down according to the level of LexA affinity for the SOS boxes. [7] Operators that bind LexA weakly are the first to be fully expressed.
SOS box is the operator to which the LexA repressor binds to repress the transcription of SOS-induced proteins. SOS boxes are found near the promoter of various genes. [1] LexA binds to an SOS box in the absence of DNA damage. In the presence of DNA damage the binding of LexA is inactivated by the RecA activator.
The prokaryotic SOS system is regulated by two key proteins: LexA and RecA. The LexA homodimer is a transcriptional repressor that binds to operator sequences commonly referred to as SOS boxes. In Escherichia coli it is known that LexA regulates transcription of approximately 48 genes including the lexA and recA genes. [62]
Normally RecA* binds LexA (a transcription repressor), activating LexA auto-protease activity, which destroys LexA repressor, allowing production of DNA repair proteins. In lysogenic cells, this response is hijacked, and RecA* stimulates cI autocleavage. This is because cI mimics the structure of LexA at the autocleavage site.
Similarly to GAL4/UAS [8] and LexA/LexAop, [9] the Q-system is a binary expression system that allows to express reporters or effectors (e.g. fluorescent proteins, ion channels, toxins and other genes) in a defined subpopulation of cells with the purpose of visualising these cells or altering their function. In addition, GAL4/UAS, LexA/LexAop ...
LexA binds to the promoter of the UmuDC operon and inhibits gene transcription. [1] DNA damage in the cell leads to the formation of RecA*. RecA* interacts with LexA and stimulates its proteolytic activity , which leads to the autocleavage of the repressor freeing the operon for transcription.
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 [9] and gene regulatory technologies including tetracycline-repressor controlled transcriptional repression [10] and the Gal4 and LexA UAS systems used in other model organisms. [11]