Constitutively active promoter

LysS/LysE an additional chloramphenicol resistant plasmid carries the gene forT7 lysozyme under constitutively active promoters. T7 lysozyme inhibits the activity of T7 polymerase thereby reducing basal (uninduced) polymerase activity/ protein expression. LysE express higher levels of T7 lysozyme for tighter control. pLacI an additional chloramphenicol resistant plasmid carries the gene for high level production of the lac repressor to reduce basal expression. 

Most of these studies have used constitutively active promoter systems in the vectors for gene activation. This approach could have a potential disadvantage because continuous production of a protein by the transgene may have adverse effects. In this regard, the development of novel regulatable vector systems that would... 

The importance of FAK is underlined by the finding that cells expressing a constitutively active form survive in suspension even though they are homeless. Here, the protein kinase is active regardless of the failure to make contact with an extracellular matrix. Rescue from apoptosis also occurs when cells express constitutively activated oncogenic forms of Ras or Src and thus activate Plj-kinase and the MAP kinase pathway. Unlike FAK, these not only prevent apoptosis but also promote proliferative signals that result in tumor formation. 

Brognard, J., Clark, A.S., Ni, Y., and Dennis. P.A. 2001. Akt/protein kinase b is constitutively active in nonsmall cell lung cancer cells and promotes cellular survival and resistance to chemotherapy and radiation. 

Clark, A.S., West, K., Streicher, S., and Dennis, P.A. 2002. Constitutive and inducible Akt activity promotes resistance to chemotherapy, trastuzumab, or tamoxifen in breast cancer cells Mol Cancer Ther 1 707-717. 

Well-documented cases exist where the estrogens inhibit the expression of some genes. These are usually transcribed by means of the constitutive activity of powerful promoters. The inhibition is a result of the steric interposition of the receptor dimer in the development region of the gene, which thereby recruits corepressors that interrupt the prior instigator effect in the absence of receptor (McKenna et al. 1999 Mester et al. 1995 Smith et al. 1997 Tora et al. 1989). 

Figure 4. Ubiquitin-mediated proteolysis regulates the onset and demise of Cdk activity during the cell division cycle. The Anaphase Promoting Complex/Cyclosome (APC/C) is active from the onset of anaphase until the end of G1 phase, during which it targets mitotic cyclins (Clbs) and other proteins such as Pdsl. The SCF complex is constitutively active but only targets Sicl and other substrates once they have been specifically phosphorylated by G1 cyclin (Cln)-Cdk (Cdc28) activity. See text for details.

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