Position-effect variegation in Drosophila melanogaster X chromosome inversion with a breakpoint in a satellite block and its suppression in a secondary rearrangement

In(1LR)pn2a is a pericentric inversion with a euchromatic breakpoint in the 2E polytene region and a heterochromatic breakpoint in the right arm of the X chromosome. It is associated with position-effect variegation (PEV) of the pn, wapl, Pgd and other vital loci of the 2E region, which are relocated near the bulk of the X heterochromatin. Cytological analysis showed that the rearrangement brings the 1A–2E euchromatic segment directly into contact with a major portion of the h34 block, a heterochromatic region that is positively stained by the N-banding technique and contains the AAGAG satellite sequences. Molecular cloning revealed the presence of a new junction between euchromatin and AAGAG satellite sequences and demonstrated that the euchromatic breakpoint of In(1LR)pn2a lies in the vinculin gene. In the X ray-induced secondary rearrangement In(1LR)r30, consisting of a pericentric inversion superimposed on In(1LR)pn2a, the h34 material remains associated with the 2E region but is separated from the rest of the X heterochromatin. In this case, the pn, wapl and Pgd loci no longer variegate, suggesting that the satellite-containing h34 region is not able per se to induce detectable PEV on the adjacent euchromatic genes. Received in revised form: 15 June 1997 / Accepted: 16 September 1997     

Concerted transpositions of mobile genetic elements coupled with fitness changes in Drosophila melanogaster

In an inbred low-activity (LA) strain of Drosophila melanogaster with a low level of fitness and a complex of inadaptive characters, in situ hybridization reveals an invariant pattern of distribution of three copia-like elements (mdg-1, mdg-3, and copia). Rare, spontaneous, multiple transpositions of mobile elements in the LA strain were shown to be coupled with a drastic increase of fitness. A changed pattern of various types of mobile elements was also observed on selecting the LA strain for higher fitness. High-fitness strains show transpositions of mobile elements to definite chromosomal sites ("hot spots"). Concerted changes in the location of three different mobile elements were found to be coupled with an increase of fitness. The mdg-1 distribution patterns were also examined in two low-fitness strains independently selected from the high-fitness ones. Fitness decrease was accompanied by mdg-1 excision from the hot spots of their location usually detected in the high-fitness strains. The results suggest the existence of a system of adaptive transpositions of mobile elements that takes part in fitness control.      

Structural organization and diversification of Y-linked sequences comprising Su(Ste) genes in Drosophila melanogaster.

Expression of the X-linked repeated Stellate (Ste) genes, which code for a protein with 38% similarity to the beta-subunit of casein kinase II, is suppressed by the Su(Ste) locus on the Y chromosome. The structure and evolution of the Y-linked repeats in the region of the Su(Ste) locus were studied. The 2800 bp repeats consist of three main elements: the region of homology to the Ste genes, an adjacent AT-rich, Y-specific segment, and mobile element 1360 inserted in the Ste sequence. Amplification of repeats was followed by point mutations, deletions, and insertions of mobile elements. DNA sequencing shows that these repeats may be considered as Ste pseudogenes or as damaged variants of a putative gene(s) encoding a protein quite different from the Ste protein as a result of an alternative splicing pattern. A comparison of 5 variants of the Y-Su(Ste) repeats shows a number of recombination events between amplified and diverged sequences that could be due to either multiple unequal mitotic sister-chromatid exchanges or to gene conversion. It is a first demonstration on a molecular level of these processes occurring in heterochromatic non-rDNA tandemly organized sequences in an eukaryotic genome.     

Optimization of solubilization and purification procedures for the hydroxylase component of membrane-bound methane monooxygenase from Methylococcus capsulatus strain M

The hydroxylase component of membrane-bound (particulate) methane monooxygenase (pMMO) from Methylococcus capsulatus strain M was isolated and purified to homogeneity. The pMMO molecule comprises three subunits of molecular masses 47, 26, and 23 kD and contains three copper atoms and one iron atom. In solution the protein exists as a stable oligomer of 660 kD with possible subunit composition (alpha beta gamma)6. Mass spectroscopy shows high homology of the purified protein with methane monooxygenase from Methylococcus capsulatus strain Bath. Pilot screening of crystallization conditions has been carried out.     

Quinone-dependent alcohol dehydrogenases and fad-dependent alcohol oxidases

This review considers quinone-dependent alcohol dehydrogenases and FAD-dependent alcohol oxidases, enzymes that are present in numerous methylotrophic eu- and prokaryotes and significantly differ in their primary and quaternary structure. The cofactors of the enzymes are bound to the protein polypeptide chain through ionic and hydrophobic interactions. Microorganisms containing these enzymes are described. Methods for purification of the enzymes, their physicochemical properties, and spatial structures are considered. The supposed mechanism of action and practical application of these enzymes as well as their producers are discussed.