Two wobble-splicing events affect ING4 protein subnuclear localization and degradation

Area of Science:

• Molecular Biology
• Cancer Research
• Gene Regulation

Background:

• Inhibitor of growth 4 (ING4) is a candidate tumor suppressor gene.
• ING4 regulates cell growth, angiogenesis, spreading, migration, and contact inhibition.
• Four ING4 wobble-splicing isoforms arise from alternative splicing at specific tandem splice sites.

Purpose of the Study:

• To investigate the subnuclear localization of ING4.
• To determine how wobble-splicing events influence ING4 localization and stability.
• To elucidate the degradation pathway of ING4.

Main Methods:

• Analysis of ING4 subcellular localization using microscopy.
• Investigation of wobble-splicing events at the exon 4-5 boundary.
• Assessment of ING4 degradation via the ubiquitin-proteasome pathway.

Main Results:

• ING4_v1 translocates to the nucleolus, indicating an intrinsic nucleolar localization signal.
• Wobble-splicing events at the exon 4-5 boundary displace ING4 from the nucleolus to the nucleus.
• ING4 is degraded via the ubiquitin-proteasome pathway, with N-terminal ubiquitination.
• Nucleolar accumulation of ING4 prolongs its half-life, while impaired nucleolar targeting increases degradation.

Conclusions:

• Wobble-splicing events at the exon 4-5 boundary are critical regulators of ING4 subnuclear localization.
• Subnuclear localization of ING4 directly influences its protein degradation rate.
• These findings highlight a novel mechanism controlling ING4 stability and function in cancer suppression.