Expression of GFP from the hsp70 promoter was observed even in the absence of heat shock, possibly because this promoter allows basal level of expression.
Therefore, it is speculated that this format allows the maintenance of basal levels of bacterioferritin inside the pathogen so that any amount of excess Fe can be immediately stored in a bound form [ 64].
In addition, the difference in background currents detected by active and null sensors in vivo under identical conditions may also allow an estimate of basal levels of neurochemicals, a measure rarely achievable in most electrochemical studies.
The high sensitivity of the Annexin V assay allowed the detection of increased basal levels of apoptosis even in untreated SKBR3 ATG7-depleted cells, although not statistically significant.
In axon guidance, Netrin binding to DCC in the growth cone leads to rapid endocytosis and degradation of DCC, which is thought to desensitise the growth cone, allowing it to adapt to increasing basal levels of a ligand as it moves up a concentration gradient (Piper et al., 2005).
This ensures basal levels of expression, thereby allowing handlers to select single copy to multicopy strains by plating the transformants directly on low concentrations of Zeocin™ (i.e., 25 μg/ml for single copy and up to 400 μg/ml for multi-copy transformants).
In a dual-solution task, which allows both spatial and response navigational learning strategies, studies in rodents showed increased basal levels of acetylcholine in the hippocampus of rodents prior to the spontaneous use of the spatial strategy.
Sas2 antagonizes Sir2, a prominent histone deacetylase involved in aging, and its deletion stabilizes Sir2 levels in aging cells, thereby allowing a low basal level of acetylation on specific histone residues associated with longevity regulation (Raisner & Madhani, 2008).
Activation of Cdx2 requires release from basal repression; Nanog [ 30] and Oct4 [ 31] repress basal levels of Cdx2 and induction of higher levels of Cdx2 by Tead4/Yap overcomes this repression, allowing Cdx2 to play its role [ 28].
It is also known that basal levels of p21CIP1/WAF1 are required to promote TGFβ-mediated cell cycle arrest, whereas a lack of p21CIP1/WAF1 allows the induction of cell proliferation in response to TGFβ [ 49].
