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I F Zhimulev

Publications and source records attributed to I F Zhimulev.

At least 91 records · Page 5Linked to original sources
PubMed1989

[Changes in the properties of intercalary heterochromatin in Drosophila melanogaster induced by position effect modifiers].

Compaction of chromosome regions translocated to the pericentric heterochromatin and the break frequency in intercalary heterochromatin (IH) regions as affected by position effect modifiers (low temperature, removing the Y chromosome, genetic enhancers and suppressors) were studied. It has been shown that the factors enhancing compaction also increase the break frequency in IH regions. Data obtained are discussed from the point of view of proteins affecting the compaction of intercalary and pericentric heterochromatin regions translocated to heterochromatin under position effect.

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PubMed1989

[Characteristics of structures of Drosophila polytene chromosomes formed by transposable DNA fragments].

An electron microscopic analysis of regions of Drosophila melanogaster polytene chromosomes into which DNA fragments of different genetic composition were inserted by the P element-mediated transformation was performed. In 4 of 5 regions studied with integrated DNA sequences of the hsp28-ry, hsp70-Adh, ry-hsp70-beta-gal genes new bands appeared. Apparently their generation is mainly caused by integration of the DNA fragments in interbands. Absence of a new band in transformed region in one of the stocks can be explained by fusion of the insertion with a band existed in the initial untransformed stock. Among the transformants studied, the minimum length of DNA fragment revealed as a new band is about 5 kb. DNA packing ratio of such the bands varies from 30 to 50. The activation of the inserted genes by heat shock allows to trace peculiarities of the new bands puffing. The puff sizes correlate with the length of the activated genes. If the DNA of the fragment consists of the sequence of one gene, its activation will lead to decondensation of the whole band. In the case when DNA fragment consists of 2 genes and the promoter of activated gene is situated inside the sequence, the band is splitted after gene activation at the beginning and then separated portion of the band is decondensed and puffed. The data obtained evidence that a band of polytene chromosome is not a unit of decondensation. DNA packing ratio in puffs is equal to 1.5-3.5.

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PubMed1988

Intercalary heterochromatin in Drosophila. III. Homology between DNA sequences from the Y chromosome, bases of polytene chromosome limbs, and chromosome 4 of D. melanogaster.

Molecular and cytogenetic characteristics are given of a 2846 bp DNA sequence from the YDm12 clone, previously derived from the long arm of the Drosophila melanogaster Y chromosome. Sequence analysis revealed within it a 1176 bp fragment with 37 bp terminal inverted repeats, flanked by 6 bp direct repeats. This fragment (called "element 1360") appeared to be A-T rich, and was saturated with short direct and inverted repeats of different degrees of homology and consensus sequences for transcription, potential Z-DNA transition and autonomous replication. After in situ hybridization to polytene chromosomes, the element 1360 exhibited variable, strain-specifics location in the euchromatic parts of the chromosome arms, but constant heavy labelling of the X chromosome region 12E1-2, autosomal regions 42B1-3, 52A1-2, 62A1-2, 75B, 82C1-3, chromosome bases, the chromocentre and numerous sites of chromosome 4. The possible role of element 1360 in heterochromatin organization is discussed.

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PubMed1988

Cytogenetic and molecular aspects of position effect variegation in Drosophila melanogaster. II. Peculiarities of morphology and genetic activity of the 2B region in the T(1;2)dorvar7 chromosome in males.

The peculiarities of compact blocks appearing as a consequence of position effect variegation were studied in male polytene chromosomes. In T(1;2)dorvar7/Y males the frequency of nuclei with a block in the 2B region was lower at all temperature and the chromosome region involved in compaction was shorter than in T(1;2)dorvar7/FM6 females. The fraction of nuclei with blocks was considerably increased in dorvar7/0 males, especially at 18 degrees C when the viability of these males is sharply reduced. The following features distinguish the blocks in males from those in females: (i) compaction of the 2B region in the males results in genetic inactivation only to a very small extent; (ii) the structure of the blocks in males is diffuse; and (iii) the male blocks still maintain some transcriptional activity as indicated by 3H-uridine incorporation. The temperature-sensitive period of both block formation and genetic inactivation was found to be during the first 3 h of embryonic development.

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PubMed1988

Trans-regulation of ecdysterone-induced protein synthesis in Drosophila melanogaster salivary glands.

A set of coordinately expressed genes is actively transcribed after a dramatic increase in the ecdysterone titer in late third-instar development of Drosophila melanogaster, as shown by the appearance of a number of puffs in salivary gland chromosomes and by the synthesis of a number of new proteins. Previous work has suggested that a product of the ecs gene, which is located within the 2B3-5 puff, is necessary for providing alterations in transcriptional activity at the sites of ecdysterone-dependent puffs. The experiments reported here were designed to determine whether the ecs gene's regulatory effect on puffing is confirmed by its regulatory effect on the synthesis of ecdysterone-inducible proteins (EIPs). The first series of experiments showed that in salivary glands in vivo ecdysterone induces 24 EIPs and in vitro induces 26 EIPs. The sets of polypeptides revealed are in good conformity. The second set of experiments demonstrated that mutations in the ecs locus disturb EIP synthesis: ecsl(1)t10 and ecsl(1)t143 mutations affect EIP synthesis to a lesser extent, while ecsl(1)t435 and ecsl(1)t324, as well as the 2B3-5 puff deficiency, prevent EIP synthesis completely. The experiments on dosage dependency revealed two EIPs whose rate of synthesis correlates with the dosage of the 2B3-5 X-chromosomal region. These EIPs are shown to be in fact small heat-shock proteins 23 and 28K, which are known to be encoded within the 67B puff and are under dual control--transient and developmental. The final set of experiments followed the 2B3-5 dosage dependency in vitro and showed that 15 EIPs display either an affected rate of synthesis or, mainly, a quicker induction time. Data obtained show that the ecs locus is trans-regulatory and that its product is necessary for spreading the effect of ecdysterone to other loci.

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PubMed1988

[Effect of transcription inhibitors on RNA synthesis in the polytene chromosomes of Drosophila melanogaster].

The inhibition of RNA synthesis by DRB (5,6-dichloro-1-beta-D-ribofuranosyl benzimidazole) differs in different regions of D. melanogaster polytene chromosomes. In the majority of regions RNA synthesis is greatly inhibited, but in certain regions, including different development stage-specific puffs, it is still on. A case of transcription initiation in the heat shock puffs was also found. alpha-Amanitin considerably reduced RNA transcription in the majority of nuclei but some part of the nuclei are not affected at all. A combined action of alpha-amanitin and DRB exerts a considerably higher inhibitory effect.

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PubMed1987

[Expression of the quantitative trait radius incompletus, temperature effects and localization of mobile genetic elements in Drosophila. II. Mobile genetic elements Dm-412].

Two "selection" sub-populations (ris- and ris+), as well as two "temperature" ones (ric113 and ric149) were earlier developed from the control ric sub-population with interrupted vein of the fly wing. All five sub-populations were investigated for hybridization of MGE Dm-412 with drosophila polytene chromosomes in situ. The tree of similarity of MGE Dm-412 hybridization patterns was built by the methods of matrix clusterization. The sub-populations with the most resembling expressions of characters (ris- and ric113, ris+ and ric149) were found to be also most similar in patterns of MGE localization and their changes. Nonrandomness of these changes was shown, the similarity of patterns being demonstrated to be mainly the result of the changes. There is evidence that such effects cannot be accounted for by genetic drift and independent stochastic changes in MGE localization.

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PubMed1985

Electron microscopical analysis of Drosophila polytene chromosomes. II. Development of complex puffs.

Data are presented of electron microscopic (EM) analysis of consecutive developmental stages of Drosophila melanogaster complex puffs, formed as a result of simultaneous decondensation of several bands. EM mapping principles proposed by us permitted more exact determination of the banding patterns of 19 regions in which 31 puffs develop. It is shown that 20 of them develop as a result of synchronous decondensation of two bands, 7 of three and 4 of one band. Three cases of two-band puff formation when one or both bands undergo partial decondensation are described. In the 50CF, 62CE, 63F and 71CF regions puffing zones are located closely adjacent to each other but the decondensation of separate band groups occurs at different puff stages (PS). These data are interpreted as activation of independently regulated DNA sequences. The decondensation of two or three adjacent bands during formation of the majority of the puffs occurs simultaneously in the very first stages of their development. It demonstrates synchronous activation of the material of several bands presumably affected by a common inductor. Bands adjacent to puffing centres also lose their clarity as the puff develops, probably due to "passive" decondensation connected with puff growth. The morphological data obtained suggest a complex genetic organisation of many puffs.

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PubMed1985

Electron microscopical analysis of Drosophila polytene chromosomes. III. Mapping of puffs developing from one band.

Mapping of 16 regions of polytene chromosomes in which 18 one-band puffs develop was carried out with the use of electron microscopy (EM). In most cases a uniform decondensation of the whole band was observed. However, there were examples in which only a part of the band was activated (three puffs) or its right and left parts decondensed simultaneously (three puffs). Splitting of the band into two parts with their further decondensation was also found (one puff). This suggests structural and functional complexity of the bands. On the basis of the data obtained here and those published earlier, a classification of 52 puffs by the number of bands participating in their formation is given. Four classes numbering 22, 21, 7, 2 puffs, developing from 1, 2, 3 and 4 bands, respectively, are revealed. The data show that active chromosome regions are rather diverse in both the pattern of decondensation and expansion of the decondensed region, thus providing evidence of the informational complexity of the majority of active regions.

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PubMed1985

Immunofluorescence localization of DNA:RNA hybrids in Drosophila melanogaster polytene chromosomes.

Sites of transcriptional activity in the whole set of Drosophila melanogaster polytene chromosomes have been localized by means of fluorescent antibodies against DNA:RNA hybrid molecules and compared with results on 3H-uridine incorporation obtained earlier. The majority of large and small puffs with intensive 3H-uridine incorporation demonstrate bright fluorescence. Moreover, bright fluorescence is also observed for a large number of small puffs though the intensity of 3H-uridine incorporation is low. Some prominent puffs with high levels of 3H-uridine incorporation show weak fluorescence. Condensed bands, as a rule, do not show fluorescence. The regions that look like interbands under the light microscope are not real interbands, but consist of minibands visible only in the electron microscope (EM). However, a region that has been previously studied by EM and proven to be a real interband between two thick dark bands (100B3-100B4-5) showed fluorescence. These data support previous suggestions indicating a substantial contribution of transcriptional products from small puffs and interbands to the whole transcriptional system of polytene chromosomes.

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PubMed1984

Fine cytogenetical analysis of the band 10A1-2 and the adjoining regions in the Drosophila melanogaster X chromosome. III. The fate mapping of the lethal focus of the l(1)BP4 gene.

Focuses of the l(1)BP4, vermilion and sevenless genes located in the same band 10A1-2 of Drosophila melanogaster X-chromosome, have been compared. For this purpose first the fate map of the blastoderm for 60 pairs of adult cuticular landmarks has been built based on scoring 612 gynandromorphs. The location of the legs and antenna primordia has been defined more exactly as compared to analogous maps by other authors. The location of new landmarks has been carried out: mesosternal bristle, sex-comb and first tergite primordia. The focus of the l(1)BP4 gene has been determined with the help of this map on the basis of analysis of 321 mosaics. The data obtained show that the lethal focus of the gene belongs to the "bilateral domineering" type and is located in the blastula area giving rise to the nervous system, behind the region of the third thoracic ganglia origin. Beside, there is a pair of autonomous nonlethal focuses of the same gene limited by the wings' zone. The focuses of the l(1)BP4 gene do not coincide with the known focuses of vermilion and sevenless genes, which means that all three genes are active in different tissues.

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PubMed1983

Genetic interpretation of polytene chromosomes banding pattern.

This mini-review covers new data regarding the problem of the functional organization of polytene chromosomes: The localization of RNA synthesis in the polytene chromosome puffs, diffuse bands and interbands; The relative stability of banding pattern and its functional value; The informational content of bands.

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PubMed1982

Cytogenetic analysis of the 2B3-4--2B11 region of the X chromosome of Drosophila melanogaster. III. Puffing disturbance in salivary gland chromosomes of homozygotes for mutation l(1)pp1t10.

Puffing patterns have been studied both in homozygotes t10/t10, a gene located in the area of the early ecdysone puff 2B5, and in a yellow (y) control stock, at the end of the third instar and during prepupal development. In mutants t10 at the end of the third instar puffing develops normally in general, however, 21 puffs (5 early and 16 late ones) underdevelop or do not develop at all, some larval intermoult puffs regressing slower. The next cycle of puffs (mid prepupal) in mutants t10 proceeds normally, but in the late prepupal cycle 21 puffs underdevelop again or are not formed at all. A model for the induction of early ecdysone puffs is proposed, assigning a key role to the 2B5 puff product in stimulating other early puffs. It is suggested that defects in the activity of early puffs in the mutant t10 may cause underdevelopment of late puffs.

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PubMed1981

Fine cytogenetical analysis of the band 10A1-2 and the adjoining regions in the Drosophila melanogaster X chromosome. I. Cytology of the region and mapping of chromosome rearrangement.

The region 9E1-2 - 10B1-2 of the Drosophila melanogaster X chromosome was analysed under the light (LM) and the electron (EM) microscope using different fixatives and an EM map of the region was constructed. EM analysis revealed 21 bands in the region 9E1-2 - 10B1-2 instead of 36 bands in Bridges' map. This discrepancy mainly results from the fact that 14 bands indicated as "doublets" by Bridges appear as a single bands. No doublets were found in the whole 9B1-2 - 10C1-2 region after fixation of salivary glands in 3% glutaraldehyde, 3% formaldehyde and 3 : 1 ethanol-acetic acid mixture. 45% acetic acid is the only fixative which results in strongly vacuolated appearance of the bands. - The break points of 30 chromosome rearrangements in the region 9E1-2 - 10B1-2 were located under EM or LM within the limits of the EM map of this region.

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PubMed1981

Fine cytogenetical analysis of the band 10A1-2 and the adjoining regions in the Drosophila melanogaster X chromosome. II. Genetical analysis.

The X chromosome region 9F12-10A7 (7 bands removed by Df(1)VL3) was saturated with lethal, semi-lethal, visible and male sterile mutations A total of 11 complementation groups were found. In the more narrow interval of Df()1)VL1 which removes 3 bands (10A1-2, 10A3, 10A4-5) 6 loci were localised. - The band 10A1-2 consists of a sereis of 5 different subunits: (i) silent DNA where no functions were found - at the distal edge of the band; (ii) and (iii) two genes: v and 1(1)BP4; (iv) silent DNA in middle of the band, (v) locus sev on the proximal edge of the band. About 70% of the band's DNA was found to be silent. - Using the set of chromosome rearrangements removing different parts of the band it was shown that these five sequences may function independently from each other.

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PubMed1981

Cytogenetic analysis of the 2B3-4-2B11 region of the X chromosome of Drosophila melanogaster. II. Changes in 20-OH ecdysone puffing caused by genetic defects of puff 2B5.

Larvae homozygous or hemizygous for the l(1)t435 mutation located within the early ecdysteroid puff 2B5, or carrying a deletion of the 2B5 band, die at the end of the third larval instar. In the salivary gland chromosomes of these larvae only intermoult puffs are detected. If these salivary glands are incubated in vitro with 20-OH ecdysone for 6 h the intermoult puff 68 C remains large, some early puffs (74EF and 75B) are induced to 30-40% of their normal size, other early (63F) and all late puffs (62E, 78D, 82F and 63E) are not induced at all. Puff 2B5 reaches its normal size but does not regress after 6 h incubation with 20-OH ecdysone, as it does in normal stocks. The data obtained in this study show the existence of a locus (or loci) in the band (puff) 2B5 which is necessary for the normal response of the salivary gland chromosomes to the hormone 20-OH ecdysone.

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