Abstract A63: Rsf-1, a chromatin remodeling protein, interacts with shelterin protein hRap1 and induces telomere shortening

Abstract

Abstract Background: Rsf-1, a chromatin remodeling factor that forms an ISWI chromatin-remodeling complex with SNF2H, has been implicated in the oncogenesis of a variety of human cancers, yet its functions in promoting tumor development remains unclear. In this study, we found Rsf-1 interacted with hRap1, a telomere binding protein involved in telomere length regulation. We aimed at characterizing the interaction between Rsf-1 and hRap1 and exploring the effect of Rsf-1 overexpression on telomere length in ovarian cancer cells. Methods: Protein microarray and co-immunoprecipitation were employed to screen and validate Rsf-1 interaction proteins. Deletion mutants of both Rsf-1 and hRap1 were constructed to map the binding domains responsible for their interaction. To determine whether RSF complex was enriched in the telomeric regions, we performed chromatin immunoprecipitation (ChIP) -qPCR in two ovarian cancer cell lines (OVCAR3 with high RSF-1 gene amplification and Rsf-1 inducible SKOV3) with antibodies against Rsf-1 and SNF2H. A ChIP-sequencing dataset performed with Rsf-1 and SNF2H antibodies using OVCAR3 cells was also examined for enrichment of telomeric sequences. To investigate the effect of Rsf-1 overexpression on telomere length, we evaluated by qPCR the telomere length in two Rsf-1 inducible cell lines (SKOV3 and BRK). Results: We identified hRap1, a telomere binding protein, as an interaction partner of Rsf-1 by protein microarray and co-immunoprecipitation. Protein interaction domain mapping revealed that C-terminal domain of hRAP1 and PHD domains and arginine-rich region of RSF1 were critical for this interaction. Both ChIP-qPCR and ChIP-sequencing demonstrated that Rsf-1 and SNF2H were enriched in the telomeres, suggesting that RSF complex was recruited by hRAP1 to the telomeres. Induction of RSF1 expression resulted in shortened telomere length in two different cell lines. The results suggest that RSF complex may be involved in the telomere length regulation mediated by hRAP1. Conclusions: Rsf-1 interacted with hRap1 through the PHD domain and the arginine-rich region. RSF complex bound telomeres, probably through the interaction with hRap1. Rsf-1 overexpression led to telomere length shortening, which may contribute to genomic instability in cancer cells. Citation Format: Ren-Chin Wu, Bin Guan, Yusuke Kobayashi, Tian-Li Wang, Ie-Ming Shih. Rsf-1, a chromatin remodeling protein, interacts with shelterin protein hRap1 and induces telomere shortening. [abstract]. In: Proceedings of the AACR Special Conference on Chromatin and Epigenetics in Cancer; Jun 19-22, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2013;73(13 Suppl):Abstract nr A63.