The size and internal structure of a heterochromatic block determine its ability to induce position effect variegation in Drosophila melanogaster

Genetics. 2000 Apr;154(4):1611-26. doi: 10.1093/genetics/154.4.1611.

Abstract

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 approximately 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Drosophila melanogaster / genetics*
  • Female
  • Gene Rearrangement
  • Genetic Linkage
  • Heterochromatin / genetics*
  • Male
  • X Chromosome
  • Y Chromosome

Substances

  • Heterochromatin