Binding of small molecules to DNA junctions

Previous results in our laboratory suggest that the (CG) 4 segments whether present in a right-handed or a left-handed conformation form distinctive junctions with adjacent random sequences. These junctions and their associated sequences have unique structural and thermodynamic properties that may be recognized by DNA-binding molecules. This study probes these sequences by using the following small ligands: actinomycin D, 1,4-bis(((di(aminoethyl)amino)ethyl)amino)anthracene-9,10-dione, ametantrone, and tris(phenanthroline)ruthenium (II). These ligands may recognize the distinctive features associated to the (CG)4 segment and its junctions and thus interact preferentially near these sequences. Restriction enzyme inhibition assays were used to determine whether or not binding interactions took place, and to approximate locations of these interactions. These binding studies are first carried out using two small synthetic oligomers BZ-III and BZ-IV. The (5meCG)4 segment present in BZ-III adopts the Z-conformation in the presence of 50 m M Co(NH3)63+. In BZ-IV, the unmethylated (CG)4 segment changes to a non-B conformation in the presence of 50 m M Co(NH3)63+. BZ-IV, containing the (CG)4 segment, was inserted into a clone plasmid then digested with the restriction enzyme Hinf I to produce a larger fragment that contains the (CG)4 segment. The results obtained on the small oligomers and on the larger fragment for restriction enzyme Mbo I indicate that 1,4-bis(((di(aminoethyl)amino)ethyl)amino)anthracene-9,10-dione binds more efficiently at or near the (CG)4 segment. Restriction enzymes EcoRV, Sac I and Not I with cleavage sites upstream and downstream of the (CG)4 insert were used to further localize binding interactions in the vicinity of the (CG)4 insert. RNA polymerase activity was studied in a plasmid which contained the (CG)4 insert downstream from the promoter sites of SP6 and T7 RNA polymerases. Activities of these two polymerases were studied in the presence of each one of the ligands used throughout the study. Only actinomycin D and spider, which bind at or near the (CG)4 segment, alter the activities of SP6 and T7 RNA polymerases. Surprisingly, enhancement of polymerase activity was observed in the presence of very low concentrations of actinomycin D. These results suggest that the conformational features of (CG) segments may serve in regulatory functions of DNA. ^

La novela del burdel: Hacia una poetica del espacio prostibulario en la narrativa hispanoamericana

The brothel, as a ‘symbolic location’ was the object of analysis in this dissertation, ascribable to its unusual and recurrent presence in Latin American narrative. The brothel was presented as a scenario, with polyvalent implications of both the space itself, as well as the different archetypes of the characters who occupy it. ^ Our analysis showed how the brothel functions as a cultural entity, social archetype, power center, mythical place and symbolic space, where man plays out his utmost dominant self. To achieve this, the analysis focused on sifting through the concepts of machismo, economic and political power, and the configuration of the ‘house’ as emblematic elements of Latin American culture. ^ The four novels chosen to underwrite this analysis were representative of the historical time frame, from Colonial times to the present, highlighting all the most distinctive features. These, in turn, led the reader to the inescapable fact that owing to certain characteristics of Latin American culture, the brothel maintains its raison d'être as a space that represents existential situations, and that far from converting itself into an anachronism, it will continue to thrive in the most significant achievements of Latin American prose. ^