DNA and RNA content of Chironomus thummi polytene chromosomes determined by micro column gel filtration

Serfling, E.; Majorov, Vladimir I.; Mikichur, N.I.; Popova, T.G.; Sandakchiev, Lev S.

doi:10.1016/0045-6039(75)90004-4

Cited by 6 publications

(1 citation statement)

References 12 publications

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“…5). The average DNA concentration in the bands, 0.17 M nucleotide, was calculated from the known DNA content of C. thummi salivary gland chromosomes (18) and from their dimensions measured before and after squashing. We assumed that the bands, which contain 95% of the total DNA (19,20), occupy 70% of the chromosome volume (21).…”

Section: Antisera Andmentioning

confidence: 99%

Left-handed Z-DNA in bands of acid-fixed polytene chromosomes.

Arndt‐Jovin

Robert‐Nicoud

Zarling

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

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Antibodies to DNA in the left-handed (Z) conformation bind to acid-fixed polytene chromosomes of both Chironomus thummi and Drosophila melanogaster, as shown by direct and indirect immunofluorescence. Comparison of the phase-contrast, immunofluorescence, and DNA staining patterns shows a predominant localization of the antibody to the regions of high contrast and DNA density, the bands. The immunofluorescence is completely abolished by competition with polynucleotides in the Z conformation but not by those in the B form. DNase but not RNase treatment eliminates the antibody staining. Actinomycin D inhibits binding, whereas mithramycin has no effect. The highly reproducible immunofluorescence patterns obtained with the anti-Z-DNA antibodies demonstrate variations in fluorescence intensity between particular bands, which can be quantitated by laser scanning and photon counting techniques. The telomeric regions and DNA strands associated with end-to-end chromosome linkage and ectopic pairing are exceptionally bright. At saturation, average values of 1 IgG molecule per 3,000 base pairs and 1 per 15,000 base pairs are found in the intensely and weakly staining regions, respectively. An alternative statement is that the left-handed Z-DNA conformation is present at a frequency of 0.02-0.1%. The measured differences reflect variations in the local density of Z-DNA sites and not in the affinity for the specific antibody, which appears to be relatively constant throughout the chromosomes (Kd = 10 nM). These observations taken together with results of biophysical studies on the properties of Z-DNA in solution suggest that regions of DNA in the left-handed conformation could be involved in higher-order structural organization of chromosomes and possibly in modulation of their functional state.Certain polynucleotides with alternating purine-pyrimidine sequences can assume a left-handed helical conformation (Z structure) in crystals (1, 2) and in solution (e.g., refs. 3-5). In the case of poly[d(G-C)], a variety of base modifications, such as methylation (6) and bromination (7,8) and Drosophila melanogaster. Polytene chromosomes are particularly suitable for in situ cytological studies due to their size, the amplification of the DNA sequences, the constancy of their banding pattern, and the structural differences between active and inactive regions.Our results, obtained with fixed polytene chromosome preparations, differ from those of Nordheim et al. (16), who reported that the immunofluorescence is restricted to interband regions. We provide additional information regarding the localization of Z-DNA-rich regions in chromosomes. These data (see also ref. Cytological Preparations. Polytene chromosomes were prepared as squashes from 4th instar larvae of C. thummi thummi and 3rd instar larvae of D. melanogaster by explantation of the salivary glands, fixation for 1 min in freshly prepared solutions of ethanol:acetic acid, 3:1 (vol/vol), and then 5 min in 45% (vol/ vol) acetic acid (or, alternatively, fixation in 45% ac...

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Section: Antisera Andmentioning

confidence: 99%

Left-handed Z-DNA in bands of acid-fixed polytene chromosomes.

Arndt‐Jovin

Robert‐Nicoud

Zarling

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

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The repetition frequency of DNA in Balbiani ring 2 of Chironomus thummi

Wobus

Serfling

1977

Chromosoma

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The RNA of Balbiani ring BR2 of polytene chromosomes from Chironomus thummi salivary glands was microisolated and reassociated in the presence of an excess of total larval DNA. BR2 RNA reacts as a single component with a C0t 1/2 of 8.6. Ribosomal precursor RNA from microisolated nucleoli reassociates under identical conditions with a C0t 1/2 of 12.3. These C0t 1/2-values suggest repetition frequencies in the range of 35 and 50 for ribosomal DNA and Balbiani ring 2 DNA, respectively. The data presented here favour the view that the gene for BR2 RNA of C. thummi is internally repeated and contains only one type of DNA sequence.

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Morphology and Structure of Polytene Chromosomes

Жимулев

1996

Advances in Genetics

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DNA and RNA content of Chironomus thummi polytene chromosomes determined by micro column gel filtration

Cited by 6 publications

References 12 publications

Left-handed Z-DNA in bands of acid-fixed polytene chromosomes.

Left-handed Z-DNA in bands of acid-fixed polytene chromosomes.

The repetition frequency of DNA in Balbiani ring 2 of Chironomus thummi

Morphology and Structure of Polytene Chromosomes

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