Tip60 Tumor Suppressor Requires Its NLS Motif to Interact with Importin <i>α</i>

Abstract

Tip60 is a specific member of MYST (Moz-Ybf2/Sas3-Sas2-Tip60) family of nuclear histone acetyltransferases (HAT). It is essential for cellular survival, differentiation, and metabolism. A putative canonical NLS motif between the chromo domain and the zinc finger of Tip60 was identified. Here we show evidence that Tip60 is associated with importin α as its substrate and transported from cytoplasm to the nucleus. Pull down assay revealed that Tip60 was physically associated with importin α both in vivo and in vitro. Confocal microscopic observation showed that Tip60 and importin α were co-localized with each other. The localization of Tip60 to the nuclear and its interaction with importin α was disrupted when its putative NLS motif for binding to importin α was mutated (219 RKRK 222  219 AAAA 222). However, attachment of this putative NLS motif to a cytoplasmic protein (YAP 1-210 fragment) promoted its nuclear localization. Based on transient transfection, Tip60 NLS motif mutant showed a substantial reduction in self-acetylation, HAT activity, and apoptotic ability whereas wild type Tip60 did not show such reduction. Taken together, our results demonstrate that importin α transports Tip60 from the cytoplasm to the nucleus through binding to the putative NLS motif of Tip60 for its tumor suppressing function.

Autoacetylation-mediated phase separation of TIP60 is critical for its functions

“…We found that lysine 187 is important for TIP60's translocation into the nucleus and its oligomerization. Since a previous report had predicted that TIP60 contains a putative nuclear localization signal (NLS) and interestingly, their anticipated NLS also included lysine 187 site 55 thus we can speculate that the autoacetylation of lysine 187 may induce local structural modifications in its IDR which my expose its NLS region critical for translocating TIP60 inside the nucleus. A previous example of similar kind shows, acetylation of lysine within the NLS region of TyrRS by PCAF promote its nuclear localization 56 .…”

“…We found that lysine 187 is important for TIP60's translocation into the nucleus and its oligomerization. A previous report had predicted that TIP60 contains a putative nuclear localization signal (NLS) and their anticipated NLS also included lysine 187 site 55 . However, the TIP60 mutant used in that study included three lysine mutations (located within putative NLS region) and in our analysis we did not found any impact of lysine 189 mutation on TIP60's nuclear import and phase separation present within that predicted NLS region (Figure 2E).…”

“…Similarly, p53 which plays an important role in maintaining genomic integrity has been shown to form amyloid in human, mouse and rat cancer tissues 55 . In addition, amyloid formation promoted by cancer-associated mutations have also been found to impair the normal function of p53 in the cell 63 .…”

“…Overexpression of SRSF1 (a component protein of NS) protein in breast cancer has been shown to be able to transform mammary epithelial cells and promote mammary gland tumorigenesis in mice 62 . Similarly, p53 which plays an important role in maintaining genomic integrity has been shown to form amyloid in human, mouse and rat cancer tissues 55 . In addition, amyloid formation promoted by cancer-associated mutations have also been found to impair the normal function of p53 in the cell 63 .…”