Characterization of Diverse Functions of NRF1 Nuclear Localization Sequence

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Transcription factors utilize nuclear localization signals (NLS) for nuclear import.
• Bipartite NLS, featuring two basic boxes separated by a spacer, are found in some nuclear proteins.
• The precise role of the spacer in bipartite NLS remains unclear.

Purpose of the Study:

• To investigate the function of the bipartite NLS in the transcription factor NRF1.
• To elucidate the role of the NLS spacer in NRF1's nuclear translocation and transcriptional activity.

Main Methods:

• Functional dissection of NRF1's bipartite NLS.
• Analysis of NLS basic box and spacer deletions.
• Assessment of NRF1 subcellular localization and transcriptional activity.
• Investigation of phosphorylation within the NLS spacer.

Main Results:

• The NRF1 NLS spacer is dispensable for nuclear translocation but essential for transcriptional activation.
• A single N-terminal basic box is sufficient for NRF1 nuclear import.
• Phosphorylation within the spacer, alongside other posttranslational modifications, regulates NRF1 nuclear translocation.
• A novel downstream target of NRF1, ZNF777, was identified.

Conclusions:

• The NRF1 NLS spacer plays a critical auxiliary role in transcriptional regulation, not translocation.
• NRF1 nuclear import relies primarily on its N-terminal basic box.
• Posttranslational modifications, including phosphorylation in the spacer, fine-tune NRF1's nuclear import and function.