[Specific DNA sequences are associated with nuclear envelopes of pseudonurse cells in Drosophila melanogaster otu 11].

Nuclei of ovarian pseudonurse cells from the mutant strain of Drosophila melanogaster otu 11 are suitable for mapping the attachment of chromosomes to the nuclear envelope (NE). Loci in contact with the NE included region 20CD of the X chromosome, region 41 of chromosome 2, the proximal end of region 81 of chromosome 3, and region 101 of chromosome 4. In situ hybridization revealed that all 4 regions contained sequences homologous to clone lambda20p1.4. DNA of clone lambda20p1.4 was previously found to bind specifically to purified D. melanogaster lamins. These results suggest that specific DNA sequences are involved in attachment of chromosomes to NE in vivo.

[Variability of pericentromeric chromatin in chromosome 2 of ovarian nurse cells during inbreeding in Anopheles atroparvus V.Tiel]. / Izmenchivost' pritsentromernogo geterokhromatina khromosomy 2 pitaiushchikh kletok iaichnikov pri inbridinge u Anopheles atroparvus V. Tiel.

We investigated the variability of pericentromeric chromatin of chromosome 2 in ovarian nurse cells (trophocytes) in two laboratory lines of malaria mosquito Anopheles atroparvus V. Tiel and in their hybrids. One line had been raised by means of sib inbreeding, the other kept at constantly high population density. The inbreeding was shown to result in an increased percentage of chromosomes bearing an achromatinic zone in the centromeric region, which resulted in chromosome breakage. Toxicological tests demonstrated an increase in the sensitivity of the progeny of females with abnormal morphotypes of chromosome 2 to the entomopathogenic bacterium Bacillus thuringiensis israelensis. The appearance of the achromatinic zone is attributed to local chromatin underreplication accompanying chromosome polytenization. Possible reasons for this phenomenon and its implication for adaptation are discussed.

DNA from Drosophila melanogaster beta-heterochromatin binds specifically to nuclear lamins in vitro and the nuclear envelope in situ.

A DNA fragment designated lambda 20p1.4 binds in vitro to polymerized Drosophila melanogaster lamin. In situ hybridization of lambda 20p1.4 to isolated polytene chromosomes revealed localization at the chromocenter and to the 49 CD region on the right arm of chromosome 2. About 120 copies of sequences homologous to lambda 20p1.4 were detected per haploid genome. Nucleotide (nt) sequence analysis demonstrates that lambda 20p1.4 is an A + T-rich, 1327-bp fragment containing four repeated units between nt 595 and 919. Results suggest that lamin interacts with a region of lambda 20p1.4 between nt 300 and 1000. Confocal immunofluorescence co-localization demonstrates that in situ, the major locus of lambda 20p1.4 hybridization, the chromocenter, is found juxtaposed to the nuclear envelope (lamina). This is the first demonstration that a DNA sequence that binds specifically to nuclear lamins in vitro, is located at or near the nuclear envelope in situ and, presumably, in vivo.