Corepressor

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In molecular biology, a corepressor or corepressor is a substance that inhibits the expression of genes . A corepressor does not reduce the expression of genes through direct interaction with the operator (a DNA sequence next to the regulated gene), but indirectly through interaction with proteins , which in turn bind to the operator gene .

In protein synthesis by prokaryotes , the ligand of a repressor protein is called a corepressor. For example, the E. coli tryptophan repressor (trpR) is only able to bind to DNA and prevent transcription of the trp operon when it is bound to its corepressor tryptophan . Since the tryptophan repressor is inactive in the absence of tryptophan, it is called an aporepressor . Since the trp operon codes for enzymes that are involved in tryptophan synthesis, this system represents a negative feedback mechanism . One speaks of end product repression .

In eukaryotes , a corepressor is a protein that binds to transcription factors . Corepressors downregulate the transcription initiation region of a gene by recruiting histone deacetylase . This catalyzes the splitting off of acetyl groups from lysine residues of histones . This increases the positive charge on the histones, the electrostatic attraction between histones and the negatively charged DNA is strengthened, and consequently the DNA is less accessible for transcription.

literature

  1. ↑ Evans PD, Jaseja M, Jeeves M, Hyde EI: NMR studies of the Escherichia coli Trp repressor.trpRs operator complex . In: Eur. J. Biochem. . 242, No. 3, December 1996, pp. 567-75. doi : 10.1111 / j.1432-1033.1996.0567r.x . PMID 9022683 .
  2. ↑ Jenster G: coactivators and corepressors as mediators of nuclear receptor function: an update . In: Mol. Cell. Endocrinol. . 143, No. 1-2, August 1998, pp. 1-7. doi : 10.1016 / S0303-7207 (98) 00145-2 . PMID 9806345 .
  3. ^ Lazar MA: Nuclear receptor corepressors . In: Nucl Recept Signal . 1, No. Jun 12, 2003, p. E001. doi : 10.1621 / nrs.01001 . PMID 16604174 . PMC 1402229 (free full text).
  4. ^ Goodson M, Jonas BA, Privalsky MA: Corepressors: custom tailoring and alterations while you wait . In: Nucl Recept Signal . 3, No. Oct 21, 2005, p. E003. doi : 10.1621 / nrs.03003 . PMID 16604171 . PMC 1402215 (free full text).

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