Abstract
Histone chaperone ASF1A has been reported to be dysregulated in multiple tumors; however, the underlying molecular mechanism that how the abundance and function of ASF1A are regulated remains unclear. Here we report that ASF1A is physically associated with USP52, which is previously identified as a pseudo-deubiquitinase. Interestingly, we demonstrate that USP52 is a bona fide ubiquitin-specific protease, and USP52 promotes ASF1A deubiquitination and stabilization. USP52-promoted ASF1A stabilization facilitates chromatin assembly and favors cell cycle progression. Additionally, we find that USP52 is overexpressed in breast carcinomas, and its level of expression correlates with that of ASF1A. Moreover, we reveal that impairment of USP52-promoted ASF1A stabilization results in growth arrest of breast cancer cells and sensitizes these cells to DNA damage. Our experiments identify USP52 as a truly protein deubiquitinase, uncover a molecular mechanism of USP52 in chromatin assembly, and reveal a potential role of USP52 in breast carcinogenesis.
Highlights
Histone chaperone ASF1A has been reported to be dysregulated in multiple tumors; the underlying molecular mechanism that how the abundance and function of ASF1A are regulated remains unclear
The results indicate that ASF1A was copurified with a number of proteins, including chromatin assembly factor 1 (CAF1), NASP, NPM, DAXX, Codanin, TLK1, TLK2, and RIF1, most of which are known to interact with ASF1A3,26
To confirm the in vivo association of ASF1A with USP52, co-immunoprecipitation experiments were performed and the results showed that USP52 was efficiently coimmunoprecipitated with ASF1A, and vice versa (Fig. 1b)
Summary
Histone chaperone ASF1A is physically associated with USP52. In an effort to better understand the mechanistic role of ASF1A in chromatin assembly and tumorigenesis, we employed affinity purification and mass spectrometry to identify ASF1A-associated proteins. In vitro deubiquitination assays demonstrated that wild-type USP52, but not USP52/ΔUCH, was able to trim K6-, K11-, K48-, K63-, and M1-linked ubiquitin chains (Fig. 2d) Together, these results support the argument that USP52 is capable of cleaving specific types of ubiquitin linkages and it is a bona fide deubiquitinase. In vitro deubiquitination assays revealed that USP52 was able to efficiently remove K48-linked polyubiquitin linkages of wild-type ASF1A (ASF1A/wt) and ASF1A/K41R, but not that of ASF1A/ K129R (Supplementary Fig. 3f), and K48-linked polyubiquitin chains conjugated onto ASF1A/K129R was dramatically reduced comparing with that onto ASF1A/wt
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