Prokaryotes gene responses

B. The lac operon of E coli is a good model for regulation of prokaryotic gene expression in response to environmental cues (Figure 12-4). 

The genetic information (DNA) and the protein-synthesizing capability of mitochondria and chloroplasts are similar to those of prokaryotes. For example, both mitochondrial and chloroplast DNA are circular and naked (i.e., not com-plexed with histone proteins as nuclear DNA is). (There is insufficient genetic information on these chromosomes to account for all organelle components. However, the nuclear genes that are responsible for synthesis of mitochondrial components resemble prokaryotic genes.)... 

In addition to HMG-CoA synthase, involved in ketogenesis, genes involved in fatty acid activation, like acyl-CoA synthetase," or in p-oxidation, like medium-chain acyl-CoA dehydrogenase are also target of PPAR. This transactivation pathway is reminiscent of a prokaryotic operon organization, in which fatty acids induce the expression of the genes responsible for their metabolism. We speculated that the main control step in fatty acid P-oxidation, the outer membrane component of carnitine palmitoyltransferase enzyme system, CPT I, could also be a PPAR target. 

Activator proteins (and a few repressors) are important in eukaryotes, as they are in prokaryotes. The DNA sequences to which activator proteins bind in eiikaryotic DNA are called response elements. A few response elements are located within the promoter region (upstream promoter elements [UPE]), but most are outside the promoter and often clustered to form an enhancer region that allows control of gene expression by multiple signals (Figure 1-5-4). 

Viruses Shunt that prevents transfer of organic carbon and nutrients to higher trophic levels Infects prokaryotes and eukaryotes sometimes very specific to host. Thought to be responsible for lateral gene transfer... 

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