Secondary structure-stretched forms of long intron RNA products from the view point of initiation of chromosome homologs somatic pairing.

In different types of chromosome pairing (meiotic, somatic, and sister chromatids pairing) initiation stages are less elucidated. In somatic homolog pairing initiation, the long intron RNA products interference may play the essential role. The strongest somatic pairing in Drosophila melanogaster 28B1-B2 locus and its enrichment by long bi-directional transcripts prone us to analyze the pre-mRNA secondary structures. The comparison of sense (pre-mRNA) and antisense (lncRNA) portions corresponding to the lengthy introns for some others' genes loci reveals the significant correlation of stretched folding form lengths with the homologue pairing percentage. Also for 28B1-B2 locus, the most significant homologue pairing is justified by the plurality of sense and antisense RNA variants for lengthy introns. The stretched forms of long intron products with multiple stem-loop clusters widely presented for sense and antisense strands may interact by multiple loops during transcription being connected to different chromosomes and hypothetically may serve for the pairing initiation. Stretched rod-like or V-shape-like are dominating forms for the whole intron RNA products or their central portions while predominantly star-like for others intron fragments.

Large-scale periodicity of nucleosome positioning signal in pericentric regions of chromosomes (Drosophila melanogaster).

Nucleosome positioning signal (NPS) in heterochromatin is not uniform. We suggest the analysis of its heterogeneity by correlation with periodic function (analog of Furrier analysis). It was established the periodical repetition of the nucleosome clusters of large size in pericentric regions in a discontinuous manner. In the 3L pericentric region, it was revealed the domination of 78-85 kbp wavelength in the correlation coefficient profile and also strong presentation of 50 kbp signal. In further to centromere position, the 69 kbp value strongly dominates as well as the 50 kbp value in the closest proximity. In addition to the long wavelength signals, there are plenty of short wavelengths signals especially in the closest vicinity to centromere. In some positions throughout pericentric region of 2L chromosome, there are two sizes of repeated intermingled correlation signals (50, and 75 kbp) with dominating value of 75 kbp in proximity and 50 kbp distantly to centromere, the situation for 2R is analogous. Some genes with long introns support these quantitative characteristics of NPSs and to some extent their dominating character in each region. The characteristic repeat periods for 3L pericentric region coincide with the distances between heterochromatin epigenetic mark clusters and their distribution throughout this region for fly embryos, larvae, and some cell lines.

Analysis and development of the computer methods of nucleosome localization on DNA fragments with different AT-content.

Trinucleotide parameter sets published previously were used for the development of the predictive method for the determining the nucleosome positions along the DNA. The choice of the type of parameter sets used depends upon AT-content of the fragment. Some limitations are imposed on these predictions due to the presence of A(n), T(n) tracts (in our case n>5 or =5) within the 145 bp fragment leading to the displacement or even the prohibition for the corresponding site to be occupied by nucleosomes. The predicted nucleosome positioning site with the large potential may influence on the choice of the proximal nucleosome positions with the weaker bending potentials as is revealed by the comparison with the micrococcal nuclease digestion map. Trinucleotide methods may be considered as advantageous in the comparison with the dinucleotide ones.

Small circles of helical DNA obtained on the basis of transcriptional pause sites sequence.

The 21-base pair synthetic DNA duplexes with basic 'pause-motif site ('CATGC') were ligated head-to-tail to produce linear and circular multimers. This also was done from other closely related sequences. Electrophoretic mobilities of the linear multimers in polyacrylamide gels were determined under the standard and modified conditions. We revealed that small linear multimers (approximately 90 bp) were characterized by comparable value of gel retardation relative to the well known curved DNA, while longer multimers (130 to approximately 170 bp) had only slightly expressed mobility anomaly. Nevertheless these multimers containing nontruncated 'pause-motif were capable of cyclization, in particular, formation of unusually small circles while truncated ones were not. We conclude that basic 'pause-motif site increases the closure ability while the multimers based on truncated 'pause motif fail to curve into the small circles. We tend to explain this situation as a result of intrinsic bending as well as the influence of the thermal fluctuations of DNA, the latter most probably can be associated with 'pause motif'. We have estimated the equilibrial and maximal bend angles per 10.5 bp to be 12 degrees to approximately 16 degrees and 32 degrees accordingly under experimental conditions of our study.

Nucleotide sequence statistical analysis of pauses in RNA elongation by Escherichia coli RNA polymerase.

A convenient motif-searching program has been developed, based on a double correlation algorithm, for analysis of the pulse character of Escherichia coli transcription. Activity in the zone of minimal pause formation (-1,2 bp) is precisely determined. Oligonucleotides (di-, tri- and tetranucleotides) are randomized by their pause-generating activity. 'CATG' and 'CATGC' are detected which coincide with the primary structure of RNA associated with distinctive delays in biologically meaningful situations.