Identification of a larger form of the histone acetyl transferase Tip60

The histone acetyl transferase Tat interactive protein 60kD (Tip60) plays major roles in the cellular response to extra- or intra-cellular signalling. Tip60 activity appears to be tightly regulated in cells through post-translational modifications or subcellular localisation of the protein. In addition, several alternatively spliced forms of Tip60 have been described. We found here that in a significant proportion of cytoplasmic poly adenylated Tip60 mRNAs, the intron 1 was not excised. Translation of this mRNA would predictably lead to the production of a longer Tip60 protein, containing a 33 amino acids insertion four amino acids after the ATG. By transient transfection experiments, we could demonstrate that this protein was significantly produced. Thus, taken together, our results indicate the existence of a longer Tip60 protein. Whether this protein could be differentially regulated and could play different roles than the classical Tip60 protein is an intriguing possibility.