p270 is an integral member of human SWI-SNF complexes, first identified through its shared antigenic specificity with p300 and CREB binding protein. The deduced amino acid sequence of p270 reported here indicates that it is a member of an evolutionarily conserved family of proteins distinguished by the presence of a DNA binding motif termed ARID (AT-rich interactive domain). The ARID consensus and other structural features are common to both p270 and yeast SWI1, suggesting that p270 is a human counterpart of SWI1. The approximately 100-residue ARID sequence is present in a series of proteins strongly implicated in the regulation of cell growth, development, and tissue-specific gene expression. Although about a dozen ARID proteins can be identified from database searches, to date, only Bright (a regulator of B-cell-specific gene expression), dead ringer (a Drosophila melanogaster gene product required for normal development), and MRF-2 (which represses expression from the cytomegalovirus enhancer) have been analyzed directly in regard to their DNA binding properties. Each binds preferentially to AT-rich sites. In contrast, p270 shows no sequence preference in its DNA binding activity, thereby demonstrating that AT-rich binding is not an intrinsic property of ARID domains and that ARID family proteins may be involved in a wider range of DNA interactions.SWI-SNF complexes were first identified in yeast cells, where they are involved in the regulation of an array of inducible genes including those required for the mating type switch and sucrose fermentation pathways (16, 28). More-recent studies suggest that these complexes have a more general role in the regulation of gene expression. The isolation and characterization of Drosophila melanogaster and mammalian homologs of many of the yeast complex members suggest that SWI-SNF complexes play fundamental roles in the regulation of gene expression during cell growth and development in all organisms (reviewed in reference 14; 17).Although SWI-SNF complexes have demonstrated DNA binding capabilities (29), the source of this activity in the complexes remains unclear. The only DNA binding protein identified to date in mammalian SWI-SNF complexes is BAF-57, which has a DNA binding activity restricted to four-way junction DNA. SWI-SNF complexes lacking a functional BAF-57 retain DNA binding activity, indicating that other DNA binding components must be present (41).p270 is an integral member of human SWI-SNF complexes, first identified through its shared antigenic specificity with p300 and CREB binding protein (CBP) (5, 6). The p300/CBP/p270 cross-reactive antibodies coprecipitate a series of proteins that includes the mammalian SWI-SNF complex components BRG1, BAF-170, BAF-155, and hSNF5/Ini1. Conversely, antibodies directed against the individual human SWI-SNF complex components BRG1 and BAF-155 immunoprecipitate p270, as demonstrated by reactivity with a p270-specific antibody (6). The sequence of p270 described here indicates that this protein contains a highly conserved...

p300 and the closely related CREB binding protein (CBP) are transcriptional adaptors that are present in intracellular complexes with TATA binding protein (TBP) and bind to upstream activators including p53 and nuclear hormone receptors. They have intrinsic and associated histone acetyltransferase activity, suggesting that chromatin modification is an essential part of their role in regulating transcription. Detailed characterization of a panel of antibodies raised against p300/CBP has revealed the existence of a 270-kDa cellular protein, p270, distinct from p300 and CBP but sharing at least two independent epitopes with p300. The subset of p300/CBP-derived antibodies that cross-reacts with p270 consistently coprecipitates a series a cellular proteins with relative molecular masses ranging from 44 to 190 kDa. Purification and analysis of various proteins in this group reveals that they are components of the human SWI/SNF complex and that p270 is an integral member of this complex.The cellular protein p300 is a direct target of the transforming functions of the adenovirus E1A gene (19, 51) and as such is implicated in the regulation of both cell cycle-specific and tissue-specific gene expression (18,27,38,43,46,52,54). p300 is highly homologous (about 64% identical) to the cyclic AMP response element binding protein (CREB) coactivator, CBP (CREB binding protein) (5,11,17,30,34). Both p300 and CBP are present in intracellular complexes with the TATA binding protein (TBP) (1, 13). Both act as cofactors for p53 (6,21,33,44) and nuclear hormone receptors (9,24,28). Both also contain intrinsic and associated histone acetyltransferase (HAT) activity (39, 53), suggesting that chromatin modification is an essential part of their role in regulating transcription.A recent detailed characterization of a panel of antibodies raised against a mixture of native p300 and CBP revealed the existence of a 270-kDa cellular protein, distinct from p300 and CBP but sharing at least two independent antigenic determinants with p300 (13). Four of the eleven antibodies in the panel recognize p270. The subset of p300/CBP-derived antibodies that recognizes p270 consistently coprecipitates a series of cellular proteins with relative molecular masses ranging from 44 to 190 kDa. Typical of these is the antibody designated NM1, whose immunoprecipitation pattern is shown in Fig. 1. TBPspecific antibodies coprecipitate a subset of these proteins including p300, CBP, and the phosphoprotein species indicated in Fig. 1 as p64 and p59 (1, 13). Because the TBP-specific antibodies do not coprecipitate all of the p300 family-associated proteins, it is likely that the array of proteins seen in Fig. 1 represents more than one intracellular complex.We have now identified four of the remaining p300/CBP/ p270-associated proteins as members of another important cellular complex: the mammalian SWI/SNF complex. The 190-kDa protein visible in the p300-related complex is BRG1, the human homolog of the yeast transcriptional activator, SWI2/ SNF2. The 170-and 155-k...

With increasing problems of decreased efficacy, toxicity and environmental degradation due to the use of chemical fungicides, there is urgent need for developing alternative strategies for managing crop diseases. One approach currently being explored is the application of safe organic-based compounds to prime the defence systems of plants in order to prevent or limit infections by pathogens. Chitosan, a deacylated derivative of chitin, is one of the compounds known to promote plant defence and growth, but the mechanisms by which it is able to do so are still unclear. This study investigated the ability of a commercial chitosan extract (Armour-Zen ® ) to reduce disease incidence and induce the production of enzymes and expression of marker genes involved in plant defences for two important tomato pathogens, Alternaria solani and Xanthomonas vesicatoria. Foliar spray applications of the chitosan extract significantly reduced the incidences of both diseases in greenhouse and field grown tomato plants and also displayed a positive effect on growth and yields of tomato fruits. Chitosan-treated plants recorded elevated levels of defence enzymes and upregulation of the PIN II marker gene for defence signalling pathways when compared to the control. It was therefore proposed that chitosan would able to provide broad-range protection through induced systemic resistance mechanisms.

D55Q-T83A and D55Q-G94S, two pseudorevertants of the D55Q mutant OmpR, an Escherichia coli transcriptional activator, were isolated previously by R. Brissette, K. Tsung, and M. Inouye (J. Bacteriol. 173:3749-3755, 1991). These pseudorevertant OmpR proteins were purified and examined for their function as transcriptional activators in a cell-free system with an ompF DNA fragment. These proteins were transcriptionally active, even after acid treatment, whereas the wild-type OmpR was completely inactive after the same treatment. Phosphorylation of acid-treated wild-type OmpR with an EnvZ11 membrane fraction and ATP restored transcriptional activity, whereas the activities of the mutant OmpR proteins did not change after phosphorylation.