Alternative splicing reverses the cell-intrinsic and cell-extrinsic pro-oncogenic potentials of YAP1

Chi Ben,Xiaojing Wu,Atsushi Takahashi-Kanemitsu,Christopher Takaya Knight,Takeru Hayashi,Masanori Hatakeyama

doi:10.1074/jbc.ra120.013820

Chi Ben, Xiaojing Wu + Show 4 more

Open Access

https://doi.org/10.1074/jbc.ra120.013820

Copy DOI

Abstract

In addition to acting as a transcriptional co-activator, YAP1 directly mediates translocalization of the pro-oncogenic phosphatase SHP2 from the cytoplasm to nucleus. In the cytoplasm, SHP2 potentiates RAS-ERK signaling, which promotes cell proliferation and cell motility, whereas in the nucleus, it mediates gene regulation. As a result, elucidating the details of SHP2 trafficking is important for understanding its biological roles, including in cancer. YAP1 comprises multiple splicing isoforms defined in part by the presence (as in YAP1-2γ) or absence (as in YAP1-2α) of a γ-segment encoded by exon 6 that disrupts a critical leucine zipper. Although the disruptive segment is known to reduce co-activator function, it is unclear how this element impacts the physical and functional relationships between YAP1 and SHP2. To explore this question, we first demonstrated that YAP1-2γ cannot bind SHP2. Nevertheless, YAP1-2γ exhibits stronger mitogenic and motogenic activities than does YAP1-2α because the YAP1-2α-mediated delivery of SHP2 to the nucleus weakens cytoplasmic RAS-ERK signaling. However, YAP1-2γ confers less in vivo tumorigenicity than does YA1-2α by recruiting tumor-inhibitory macrophages. Mechanistically, YAP1-2γ transactivates and the YAP1-2α-SHP2 complex transrepresses the monocyte/macrophage chemoattractant CCL2 Thus, cell-intrinsic and cell-extrinsic pro-oncogenic YAP1 activities are inversely regulated by alternative splicing of exon 6. Notably, oncogenic KRAS down-regulates the SRSF3 splicing factor that prevents exon 6 skipping, thereby creating a YAP1-2α-dominant situation that supports a "cold" immune microenvironment.

Highlights

YAP1 is a transcriptional co-activator that interacts with a number of sequence-specific transcription factors, most notably TEA domain (TEAD), and thereby transactivates downstream target genes, which stimulates cell proliferation while preventing cell death [1]
To gain insights into the mechanism regulating the alternative splicing of exon 6 in YAP1 pre-mRNA, we searched for splicing factor-binding motifs in YAP1 exon 6 using the online database SpliceAid [33], and we identified SRSF3 consensus binding motifs in the database (Fig. S4A)
We examined whether SRSF3/Srsf3 was involved in the regulation of YAP1/Yap1-mediated CCL2/Ccl2 expression by measuring Ccl2 mRNA levels in NIH3T3 or Srsf3KO#1 NIH3T3 cells by quantitative RT-PCR (qRT-PCR) analysis

Summary

Introduction

YAP1 (yes-associated protein 1, and its paralog TAZ) is a transcriptional co-activator that interacts with a number of sequence-specific transcription factors, most notably TEADs, and thereby transactivates downstream target genes, which stimulates cell proliferation while preventing cell death [1]. Whereas the level of SHP2 in AGS cells was not significantly changed by YAP1 knockout, TAZ expression was slightly elevated in YAP1KO cells as previously reported (Fig. S2B) [22]. As in the case of YAP1, knockdown of Taz expression in NIH3T3 cells by specific siRNA gave rise to an increase in the level of cytoplasmic Shp2 at a low cell density (Fig. S2F), which was concomitantly associated with the increase in the active form of Erk (pErk) (Fig. S2G).

Results

Conclusion