Isha is a su(Hw) mRNA-binding protein required for gypsy insulator function.

Area of Science:

• Molecular Biology
• Genetics
• Epigenetics

Background:

• Chromatin insulators like the gypsy complex establish independent transcriptional domains.
• The noncoding su(Hw) mRNA associates with the gypsy complex, but its recruitment mechanism is unknown.

Purpose of the Study:

• To identify the protein responsible for recruiting su(Hw) mRNA to the gypsy insulator complex.
• To elucidate the function of this novel protein in insulator activity and nuclear organization.

Main Methods:

• RNA-affinity pulldown coupled with mass spectrometry to identify RNA-binding proteins.
• In vitro and in vivo biochemical assays to confirm protein-RNA and protein-protein interactions.
• Chromatin immunoprecipitation sequencing (ChIP-seq) to determine genomic localization.
• Depletion studies to assess functional impact on insulator activities.

Main Results:

• Identified Isha (CG4266) as a novel RNA-binding protein associated with su(Hw) mRNA.
• Isha interacts with RNA Polymerase II and binds chromatin at gene 5' ends.
• Isha physically associates with the gypsy insulator component CP190.
• Isha depletion impairs enhancer-blocking and barrier activities and disrupts insulator body localization.

Conclusions:

• Isha acts as a nuclear RNA-binding protein adapter, facilitating the recruitment of su(Hw) mRNA to the gypsy insulator.
• Isha is essential for maintaining gypsy insulator function and proper nuclear organization of insulator bodies.