Stress response in Drosophila subobscura: DNA‐RNA hybrids and transcriptional activity

Abstract

Immunofluorescent techniques have been used in the analysis of DNA-RNA hybrids occurrence and its relationship to transcriptional events on polytene chromosomes of Drosophila subobscura. We have studied the distribution of these hybrids on uninduced/induced chromosomes. Two different indirect immunofluorescence methods for the detection of DNA-RNA hybrids were used. Our data confirm the positive correlation between localization of DNA-RNA hybrids and transcriptional activity by following the Büsen et al procedure (1982). Using the other protocol, which allows chromosomal DNA-RNA to denature and renature, makes DNA-RNA hybrids detectable not exclusively in active chromosomal regions. Taking Büsen as method of choice, this technique allowed to localize the exact transcriptional active sites on puffs: hybrid fluorescence was restricted to marginal or central puff areas. Moreover, no correlation between fluorescence and puffs size was found. However, our studies on induced chromosomes indicate that: 1) the 15DE puff, previously described as t-puff, was not really a heat shock puff, since no transcriptional activity was detected; 2) hybrid fluorescence at 2C and 31CD regions was observed. No labelling was found in these loci in the autoradiography data, reported by other authors.

Hybridization between mitochondrial heavy strand tDNA and expressed light strand tRNA modulates the function of heavy strand tDNA as light strand replication origin

“…[23][24][25] For example, in Drosophila, DNA-RNA hybridization associates positively with gene expression. 26 Apparently, bacterial replication sometimes uses transcription-related DNA-RNA † http:/ /frontend.bioinfo.rpi.edu/zukerm/cgi-bin/rnaindex.cgi of Chlorocebus tantalus (heavy strand sequence from site 5146 to site 5176 according to annotation in Genbank NC_009748). Secondary structure from http://frontend.bioinfo.rpi.edu/ applications/mfold/cgi-bin/dna-form1.cgi.…”