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Regulatory sequences and nuclear factors governing tissue-restricted expression of the mouse arrestin gene were investigated. The results showed that while proximal promoter sequence positions -38 to +304 are sufficient to direct low levels of retina-specific gene expression, sequences extending upstream to position -209 support higher levels of expression in the retina, as well as detectable expression in the lens, pineal gland, and brain. Within the interval between positions -209 and -38, a broadly expressed nuclear factor, Bd, binds to sequences centered between positions -205 and -185, a region which contains two direct repeats of the hexamer, TGACCT. The proximal promoter binds three apparently retina-specific nuclear factors, Bpl, Bp2, and Bp3, through overlapping sequences centered between positions -25 and -15. Bpl and Bp3 also recognize a closely related sequence found in the promoter regions of several other vertebrate photoreceptor-specific genes. Moreover, the consensus binding site for Bpl, designated PCE I, is identical to RCS I, an element known to play a critical role in eliciting photoreceptor-specific gene expression in DrosophUia melanogaster. The results suggest that PCE I and RCS I are functionally as well as structurally similar and that, despite marked differences in the fly and vertebrate visual systems, the transcriptional machinery involved in photoreceptorspecific gene expression has been strongly evolutionarily conserved.

In earlier studies from this laboratory, Xanthomonas campestris pv. glycines was found to exhibit a nutrition stress-related postexponential rapid cell death (RCD). The RCD was exhibited in protein-rich media but not in starch or other minimal media. This RCD in X. campestris pv. glycines was found to display features similar to those of the programmed cell death (PCD) of eukaryotes. Results of the present study showed that the observed RCD in this organism is both positively and negatively regulated by small molecules. The amino acids glycine and L-alanine as well as the D isomers of valine, methionine, and threonine were found to induce the synthesis of an active caspase-3-like protein that was associated with the onset of RCD. Addition of pyruvate and citrate to the culture medium induced both the synthesis of active caspase-3-like protein and RCD. Higher levels of intracellular accumulation of pyruvate and citrate were also observed under conditions favoring RCD. On the other hand, dextrin and maltose, the hydrolytic products of starch, inhibited the synthesis of the caspase-3-like protein. Addition of glucose and cyclic AMP (cAMP) to the RCD-favoring medium prevented RCD. Glucose, cAMP, caffeine (a known inhibitor of a phosphodiesterase that breaks down cAMP), and forskolin (from the herb Coleus forskholii, known to activate the enzyme adenylate cyclase that forms cAMP) inhibited the caspase enzyme activity in vivo and consequently the RCD process. The addition of glucose and other inhibitors of RCD enhanced intracellular cAMP accumulation. This is the first report demonstrating the involvement of small molecules in the regulation of nutrition stress-related stationary-phase rapid cell death in X. campestris pv. glycines, which is programmed.In eukaryotes, programmed cell death (PCD) is a genetically regulated self destruction process for the elimination of damaged or unwanted cells. It plays an important role in the development and maintenance of the integrity of organisms (26,47,48). Cells undergoing PCD exhibit a number of biochemical, physiological, and morphological features (19,32). PCD in a cell is induced by a certain signal(s). The end point of the signaling activity is the induction and activation of caspases (cysteinyl aspartate-specific proteases), the proteases that finally execute PCD (8,30).Several investigators have reported the occurrence of PCD in bacteria regulated by chromosomal and extrachromosomal toxin-antitoxin pairs of molecules (9,15,18,20,35,36,45,49). In Escherichia coli, such chromosomal toxin-antitoxin systems include mazEF (9, 24, 27), chpBIK (24), relBE (16), yefM-yoeB (5, 6, 17), and dinJ-yafQ (18). In earlier studies from this laboratory, Xanthomonas campestris pv. glycines, a plant pathogen, and the etiological agent of bacterial pustule disease of soybean (Glycine max), was found to exhibit a nutritional stress-related postexponential rapid cell death (RCD). The RCD in X. campestris pv. glycines was found to display features similar to those of the programmed cell death (...

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