The role of lysine palmitoylation/myristoylation in the function of the TEAD transcription factors.

The TEAD transcription factors are the most downstream elements of the Hippo pathway. Their transcriptional activity is modulated by different regulator proteins and by the palmitoylation/myristoylation of a specific cysteine residue. In this report, we show that a conserved lysine present in these transcription factors can also be acylated, probably following the intramolecular transfer of the acyl moiety from the cysteine. Using Scalloped (Sd), the Drosophila homolog of human TEAD, as a model, we designed a mutant protein (Glu352GlnSd) that is predominantly acylated on the lysine (Lys350Sd). This protein binds in vitro to the three Sd regulators-Yki, Vg and Tgi-with a similar affinity as the wild type Sd, but it has a significantly higher thermal stability than Sd acylated on the cysteine. This mutant was also introduced in the endogenous locus of the sd gene in Drosophila using CRISPR/Cas9. Homozygous mutants reach adulthood, do not present obvious morphological defects and the mutant protein has both the same level of expression and localization as wild type Sd. This reveals that this mutant protein is both functional and able to control cell growth in a similar fashion as wild type Sd. Therefore, enhancing the lysine acylation of Sd has no detrimental effect on the Hippo pathway. However, we did observe a slight but significant increase of wing size in flies homozygous for the mutant protein suggesting that a higher acylation of the lysine affects the activity of the Hippo pathway. Altogether, our findings indicate that TEAD/Sd can be acylated either on a cysteine or on a lysine, and suggest that these two different forms may have similar properties in cells.