The Size and Internal Structure of a Heterochromatic Block Determine Its Ability to Induce Position Effect Variegation in Drosophila melanogaster

Autor: Silvia Bonaccorsi, Vladimir A. Gvozdev, Tolchkov Ev, Rasheva Vi, Thomas Westphal
Rok vydání: 2000
Předmět:
Zdroj: Genetics. 154:1611-1626
ISSN: 1943-2631
DOI: 10.1093/genetics/154.4.1611
Popis: In the In(1LR)pn2a rearrangement, the 1A-2E euchromatic segment is transposed to the vicinity of X heterochromatin (Xh), resulting in position effect variegation (PEV) of the genes in the 2BE region. Practically the whole X-linked heterochromatin is situated adjacent to variegated euchromatic genes. Secondary rearrangements showing weakening or reversion of PEV were obtained by irradiation of the In(1LR)pn2a. These rearrangements demonstrate a positive correlation between the strength of PEV of the wapl locus and the sizes of the adjacent heterochromatic blocks carrying the centromere. The smallest PEV-inducing fragment consists of a block corresponding to ~10% of Xh and containing the entire XR, the centromere, and a very proximal portion of XL heterochromatin. Heterochromatic blocks retaining the entire XR near the 2E region, but lacking the centromere, show no PEV. Reversion of PEV was also observed as a result of an internal rearrangement of the Xh blocks where the centromere is moved away from the eu-heterochromatin boundary but the amount of X heterochromatin remaining adjacent to 2E is unchanged. We propose a primary role of the X pericentromeric region in PEV induction and an enhancing effect of the other blocks, positively correlated with their size.
Databáze: OpenAIRE