Multiple Cos2/Ci interactions regulate Ci subcellular localization through microtubule dependent and independent...

Area of Science:

• Developmental Biology
• Cell Biology
• Molecular Biology

Background:

• The Hedgehog (Hh) signaling pathway is crucial for numerous developmental processes.
• In Drosophila, Hh signaling controls the activity of the Cubitus interruptus (Ci) transcription factor.
• Full-length Ci (Ci155) is normally sequestered in the cytoplasm via protein complexes.

Purpose of the Study:

• To elucidate the molecular mechanisms governing Ci155 cytoplasmic sequestration.
• To investigate the role of Costal2 (Cos2) in Ci155 localization.
• To determine the contribution of microtubules and nuclear localization signals to Ci155 retention.

Main Methods:

• Co-immunoprecipitation assays to study protein interactions.
• Analysis of Ci155 localization in Drosophila imaginal discs.
• Treatment with nocodazole to disrupt microtubules.
• Functional assays involving engineered Ci155 constructs with added nuclear localization signals (NLS).

Main Results:

• Costal2 (Cos2) binds to both the N-terminal and C-terminal domains of Ci155.
• Cos2 binding competes with Suppressor of Fused [Su(fu)] binding to Ci155's N-terminus.
• Disruption of microtubules with nocodazole promotes Ci155 nuclear translocation.
• Addition of an NLS to Ci155 facilitates its nuclear entry, suggesting NLS masking contributes to cytoplasmic retention.

Conclusions:

• Costal2 binding to distinct Ci155 domains is essential for cytoplasmic retention.
• The microtubule cytoskeleton plays a significant role in maintaining Ci155 in the cytoplasm.
• Nuclear localization signal masking is another mechanism contributing to the cytoplasmic sequestration of Ci155 in the absence of Hedgehog signaling.