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  • 1985-1989  (3)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Telomeric DNA sequences differentially activated by heat shock in two Chironomus subspecies (1988)
    Springer
    Chromosoma 96 (1988), S. 139-144 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The patterns of puffing, transcription and protein synthesis under heat shock were analysed in polytene nuclei of Chironomus thummi piger, in comparison with those obtained in the closely related subspecies C. th. thummi. Most chromosomal heat shock puffs, as well as heat shock induced polypeptides, in C. th. piger paralleled those previously reported for C. th. thummi. Nevertheless, we found a striking difference in behaviour in the induction of telomeric Balbiani rings by heat shock in the two subspecies. Although homologous sequences were present at all the telomeres in both subspecies, they were not always transcriptionally activated by heat shock. The most frequently puffed telomeres were that of chromosome III R in C. th. thummi and that of chromosome IV R in piger. Transcription of the same sequences from both telomeric Balbiani rings (T-BR-III and T-BR-IV) occurred under heat shock. The enigmatic behaviour of telomeres and the functional significance of T-BRs are discussed in relation to possible equivalents in other Diptera.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331046
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Cloning and molecular characterization of a telomeric sequence from a temperature-induced Balbiani ring (1985)
    Springer
    Chromosoma 92 (1985), S. 108-115 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In Chironomus thummi thummi a Balbiani ring-like structure is induced at the right end of chromosome III by heat shock. Telomere-specific clones were obtained by microcloning this chromosome region. One of the recombinant clones, λCthS, which had an insert of 176 base pairs (bp), hybridized in situ to all the chromosome ends of C. th. thummi except one on the acrocentric chromosome IV. Homologous sequences were also present at two interstitial sites on chromosome II. Southern analysis of genomic DNA indicated that the 176-bp insert represents a basic repeating unit clustered in tandem arrays. Around 1000 copies of this sequence were located in each telomere. The repeats were homogeneous in size but showed some sequence divergence, which seemed to increase when different telomeres were compared. At the nucleotide sequence level the most noticeable feature was the presence of tracts of adenine alternating with tracts of thymine. In situ hybridzation to chromosomal RNA showed that the 176-bp repeat was complementary to the RNA transcribed at the T-BRIII region, and occasionally, to the RNA transcribed at some of the other telomeres during heat shock. Northern blot analysis of total RNA showed that a transcript larger than 10 kilobase pairs (kb) and complementary to the teloeric insert was present in heat-shocked as well as in untreated cells. However, at most only a very weak RNA hybridization was seen at the telomeres of untreated animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328462
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Identification of the spI products of Balbiani ring genes in Chironomus thummi (1989)
    Springer
    Chromosoma 98 (1989), S. 428-432 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The spI fraction of high molecular weight secretory proteins was analysed in Chironomus thummi. These proteins are encoded by giant Balbiani ring (BR) genes which develop specifically in salivary gland cells. Each component of the spI fraction was studied electrophoretically from early and middle 4th instar larvae and prepupae, as well from galactose-treated larvae where changes in the relative puffing pattern of BR1 and BR2 are known to occur. The spI fraction consists of at least two bands with electrophoretic mobilities slower than those of the spI components of Camptochironomus. The slow migrating component remains throughout the 4th larval instar, while the amount of the faster component changes, being abundant in early 4th instar and prepupae, but not present (or very weak) in middle 4th instar. The correlated shifts in BR puffing pattern during these developmental stages suggest that the slow and fast components are encoded by BR2 and BR1. The spI fraction is modified by galactose treatment, the fast component being induced in parallel with a decrease in the slow component. These changes are correlated with changes in the steady-state levels of RNA: an increase in BR1 RNA and a decrease in BR2 RNA, and of proteins. These proteins could correspond to the spIb and spIa fractions allocated to BR2 and BR1, respectively, in Camptochironomus. After galactose treatment a new faster band sometimes appears, that could correspond to the spIc fraction of Camptochironomus. A possible spId equivalent was also identified. In conclusion the main features of the spI family in C. thummi are similar to those of spI in Camptochironomus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292788
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    Paper (German National Licenses)
    Fulltext
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