Positive-Regulatory Signals

Acdvadon of TFs is the culminadng step of several signal d ansclucdon pathways, and requires upsdream acdvity of various kinase pathways. Let s roll upwards. 

Recently, NADPH oxidase has been identified as the ROS-producing molecule in activated glial cells (Pawate et al., 2004). Cytokine stimulation of astrocytes leads to rapid activation of NADPH oxidase and release of ROS followed by expression of pro-inflammatory products like, iNOS. Consistently, attenuated expression of iNOS is observed in primary astrocytes derived from gp9F -deficient mice (Pawate et al., 2004). ROS are believed to regulate expression of pro-inflammatory gene products via NF-kB. However, the involvement of other transcription factors in ROS-mediated gliosis cannot be ruled out. 

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In hematopoietic cells, SHP2 appears to be involved in various signaling pathways (Fig. 9), with the positive regulatory role generally ascribed to activation of the ERK pathway upstream of Ras [177, 178]. This function could be mediated by inhibiting the recruitment of Ras-GAP or the DOK proteins, or more indirectly... 

Regulation of virulence as well as conjugal transfer of DNA by peptide signaling seems to be important in many G- - bacteria including bacilli that have not been discussed in this review. Bacteriocin production in LAB is considered as a positive trait in environments such as food and alimentary canal and they are often regulated by PP-dependent three-component regulatory systems. 

Nuclear receptors exert their different transcriptional functions through interactions with and the recruitment of co-factors to responsive promoters. Co-factors are either positive or negative regulatory proteins and are classified as co-activators, which promote, or co-repressors, which attenuate the activity of nuclear hormone receptors [46]. The molecular mechanisms that regulate the mutually exclusive interactions of the nuclear receptor with either class of co-factors have been analysed by crystallographic studies. Functional and structural studies have shown that co-activators interact with the transactivation function (AF) of nuclear hormone receptors via short, leucine-rich motifs (LXXLL) termed NR boxes , thereby transducing hormonal signals to the basal transcription machinery [47]. 

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