The extrachromosomal East protein of Drosophila can associate with polytene chromosomes and regulate gene expression.
The EAST protein of Drosophila is a component of an expandable extrachromosomal domain of the nucleus. To better understand its function, we studied the dynamics and localization of GFP-tagged EAST. In live larval salivary glands, EAST-GFP is highly mobile and localizes to the extrachromosomal nucleoplasm. When these cells are permeabilized, EAST-GFP rapidly associated with polytene chromosomes. The affinity to chromatin increases and mobility decreases with decreasing salt concentration. Deleting the C-terminal residues 1535 to 2301 of EAST strongly reduces the affinity to polytene chromosomes. The bulk of EAST-GFP co-localizes with heterochromatin and is absent from transcriptionally active chromosomal regions. The predominantly chromosomal localization of EAST-GFP can be detected in non-detergent treated salivary glands of pupae as they undergo apoptosis, however not in earlier stages of development. Consistent with this chromosomal pattern of localization, genetic evidence indicates a role for EAST in the repression of gene expression, since a lethal east mutation is allelic to the viable mutation suppressor of white-spotted. We propose that EAST acts as an ion sensor that modulates gene expression in response to changing intracellular ion concentrations.
Wasser
Martin
M
Bioinformatics Institute, Department of Imaging Informatics, Singapore, Singapore. martinw@bii.a-star.edu.sg
Chia
William
W
D000818:Animals; D017209:Apoptosis; D018797:Cell Cycle Proteins; D002875:Chromosomes; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*
D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; C114107:EAST protein, Drosophila; D010750:Phosphoproteins; D049452:Green Fluorescent Proteins