Alternative Splicing (AS) Provides an Alternative Mechanism for Regulating GLIS3 Expression and Activity

The Krüppel-like transcription factor GLIS3 plays an important regulatory role in the development of various tissues, both in mice and humans. Loss-of-function mutations in <i>GLIS3</i> are implicated in several pathologies, including polycystic kidney disease, diabetes, and hypothyroidism. Previous studies have reported that the mouse <i>Glis3</i> gene generates a 7524 bp mRNA encoding a 935 amino acid (aa) protein, with a homologous human protein of 930 aa. Here, we identify a shorter mouse mRNA lacking the third exon, producing a shorter 659 aa GLIS3 protein. This shorter transcript is expressed at a higher level than the longer transcript in all mouse tissues tested and produces a protein that is more stable and exhibits a greater transactivation potential. This suggests that the 276 aa N-terminus in the longer mouse GLIS3 protein encompasses important regulatory domain(s). Mass spectrometry identified several phosphorylation sites that may contribute to the post-translational regulation of GLIS3 activity and function and several known members of co-activator and co-repressor complexes, consistent with the concept that GLIS3 can act both as a transcriptional repressor and activator. These data offer important insights into how GLIS3 activity is regulated and offer potential mechanisms for its control during tissue development and disease.