Promoter locus

Expression of the lac operon is regulated by controlling elements, which are separate from the structural genes. The controlling elements consist of a promoter locus, which is the site where RNA polymerase binds and initiates transcription the promoter locus also contains sites for the binding of a repressor and an activator. The i gene encodes the repressor, and the crp gene encodes the activator. 

The core enzyme of RNA polymerase is catalytically active but lacks specificity. The core enzyme alone would transcribe both strands of DNA when only one strand contains the information in the gene. The holoenzyme of RNA polymerase binds to specific DNA sequences and transcribes only the correct strand. The essential role of the O-subunit is recognition of the promoter locus (a DNA sequence that signals the start of RNA transcription see Section 11.3). The loosely bound O-subunit is released after transcription begins and about 10 nucleotides have been added to the RNA chain. Prokaryotes can have more... 

The controlling elements of the operon consist of a promoter locus (j>), an operator locus (o), and a regulator gene (/). These will be introduced here and discussed in greater detail in Sections 111 and IV. 

The characteristics of some promoter mutants have been determined. Promoter mutants produce all three of the operon-assodated proteins at a diminished rate. Such mutants are affected in the usual way by inducers and the repressor of the lac operon, indicating that the promoter locus is involved in control processes other than those regulated by the operator and i gene product. Promoter mutations like operator mutations are cis-dominant. 

The neural structures involved in the promotion of the waking (W) state are located in the (1) brainstem [dorsal raphe nucleus (DRN), median raphe nucleus (MRN), locus coeruleus (LC), laterodorsal and pedunculopontine tegmental nuclei (LDT/PPT), and medial-pontine reticular formation (mPRF)] (2) hypothalamus [tuberomammillary nucleus (TMN) and lateral hypothalamus (LH)[ (3) basal forebrain (BFB) (medial septal area, nucleus basalis of Meynert) and (4) midbrain ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) (Pace-Schott Hobson, 2002 Jones, 2003). The following neurotransmitters function to promote W (1) acetylcholine (ACh LDT/PPT, BFB) (2) noradrenaline (NA LC) (3) serotonin (5-HT DRN, MRN) (4) histamine (HA TMN) (5) glutamate (GLU mPRF, BFB, thalamus) (6) orexin (OX LH) and (7) dopamine (DA VTA, SNc) (Zoltoski et al, 1999 Monti, 2004). 

Figure 14.2 Hypocretinergic activity dependent on the states of vigilance. During wakefulness, metabolic, circadian, and behavioral inputs converge on hypocretin neurons, which activate noradrenergic neurons in the locus coeruleus and promote arousal. During non-REM sleep, the activity of hypocretin neurons decreases, but the inhibitory influence of REM-off neurons on REM-on cells is still effective. During REM sleep, hypocretin and REM-off cells are silent, disinhibiting REM-on cells. Reprinted with permission from Sutcliffe de Lecea (2002). (See also Plate 7.)...

The G/A promoter polymorphism at the apoAI gene locus predicts individual variability in fasting and postprandial responses to the HMG CoA reductase inhibitor atorvastatin. Circulation 1999 100(Suppl I) I—239. 

Gene A segment of DNA containing all information for the regulated biosynthesis of an RNA product, including promoters, exons, introns, and other untranslated regions that control expression. Fundamental physical and functional unit of heredity and evolution. A gene is an ordered sequence of nucleotides located on a specific chromosomal locus that encodes particular products (i.e., RNA molecules, proteins) (see comment at amino acids). 

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